With much thanks to Larry III, I found my "how to." Use it as a guide. Your method may vary.
By the way, Larry III has a catogorized list of posts from the Yahoo archive (in excel format). You can go to the "Archive" button at the top of the page and use quick jump to go to the post number.
Here's my original how-to, posted just after I finished (I was so excited I'd done it, I couldn't wait) on 8/9/2000 (back in the "good ol' days.")
Okay, take a deep breath and settle in, it's a long process. You'll need the obvious tools: Ratchet, Spark Plug Socket (5/8), three inch and six inch extensions. You'll need a 12mm boxed end wrench (the longer the better). A retrieval tool (I use the claw type – the magnetic type works also) is helpful when you drop extensions, sockets, etc. A pry bar is helpful for easing out the coils (a small one with a slight bend on the flat end – I know this sounds extreme, but this was a suggestion from Danny, the Suby tech in the club). A flat bladed screwdriver is also a helpful tool. I used one to separate my ratchet from the extension so I could finish backing out the plugs by hand. You'll also need a 10 mm socket or flat wrench to remove your battery terminals.
START WITH A STONE COLD ENGINE!
To prep, begin by removing the battery. Then remove the air filter box. As I said in my other post, it is easier if you remove the entire box complete with bracket. The booger of it is, one of the bolts in the bracket also goes through the bracket of the ABS unit, but, if you just remove the bolt on that one corner, the bracket on the air box should just slide out.
I saved the worst for first (rearmost driver's side). It's in the tightest spot. Undo the 12 mm bolt that holds the coil pack. Don't pull it all the way out. Back it out until the threads begin to emerge from the coil pack housing (you'll need to pull on this to pop the coil pack out). Once the bolt has reached this point, begin to pull on the bolt. If the coil doesn't pop off, keep backing out the bolt until it does. If you back the bolt all the way out and the coil doesn't come out, then, screw the bolt back in about half way. Remember the pry bar? Take the slightly bent end and place it on the shoulder of the bolt, then, use the engine block for leverage and GENTLY pry against the bolt. It won't take much pressure to pop it out. It is very rare that they come off, but, once the coil is out, check to make sure the rubber boot is still on the end of the coil. If it isn't, you'll need to fish it out, possibly with a very long screwdriver. It'll be difficult to check this one, because there's only one place you can put it to get it out of the way, and that's to your left, up in the little recess left from pulling the coil. Try to make sure you don't stress the wires, or pry against them (coils are expensive). Also, if you have to fish out a boot, make sure you don't damage it. The only way you can replace the boot is either by knowing someone who has one, or by buying a new coil (ouch). Okay, with the coil pack out of the way, remove the access plug from the fender well (I'm going to guess after I posted about this, you went looking for it – that's what I did when they told me about it. I almost never found it, but it's there. Just look right across from the place you removed the coil – it's also interesting that this access hole is not mentioned in the service manual – the manual is totally sketchy about a plug change). You should now be able to push you wrench with a six inch extension and your plug socket through the hole in the fender well – yeah, it's a pain, but, believe me, it'll still be easier than trying to do it without it (if you need to get the tire out of the way, just jack your car up a few inches). The recess will practically guide your socket to the plug. This is where "normal" kind of takes over. Just back out the plug like you would normally. When it gets to a point where it's loose enough, take the ratchet off of the extension and back it the rest of the way with your fingers, so you can feel when it's coming out. Then, put in your fresh plug. Make sure you start the plug by using just your extension and your fingertips – you don't want to cross-thread the plug. Luckily, the plug practically threads itself if you do it gently. (Note: I did not re-gap my plugs. They came factory gapped at .040. The recommended gap is from .039 to .043. I figured .040 was good enough for "middle ground," plus, I didn't want to take a chance on damaging any of the platinum bits – they look fragile). Once you've gotten the plug as tight as you can get it with your fingers, then, attach the ratchet and tighten her down. Torque spec is 14-22 ft.lbs. I didn't use a torque wrench, I trusted my instincts. If you've changed plugs before, you can feel the "not too tight, not too loose" point. Now, all that's left is replacing the coil. Once you've taken it off, it's easy to figure out how to put it back on. Don't forget to put the access plug back in – you'd hate to be throwing water into the engine bay on rainy days.
The rest of the plugs are similar. Working toward the front, your next is a bit of a bear, but, you can use your three inch extension and the coil is easier to get out of the way. Of course, the front driver's side is the easiest. You'll have the most room here.
Moving to the other side, again, the access hole will make the work easier on the rearmost plug. The coil is easily moved out of the way. Then, if you've removed the bracket for the air box, your job should be, pretty much, cake from here on out.
Once you've gotten that first "bear" plug out, then (or this is how it worked for me), your confidence level will be up enough to complete the job.
That's about all I can think of. If you have any more specific questions, then, feel free to ask. If you get into BIG trouble, e-mail me your phone number – grab your cordless phone, and I can try to talk you through, but, I believe you'll be fine.
Again, be careful of boots, wiring, etc. Oh, and also, DO NOT put never seize on the plugs. It's a big no-no, both from Subaru and from NGK. The temperature of our engines makes the compound too hard. Pieces could possibly fall into the plug holes and into the cylinders – not good.
Let me know how it goes and, ask as many questions as you need to. I guess I can call my installation successful – I haven't blown a plug yet
Randy
FOOTNOTE: Still running strong on these very plugs.