Engine rebuild vs. replacing gaskets/seals?

[WestCoastSVX]

At 205,000 miles my SVX is coming to a crossroads. First off, it is not a question of keeping it or getting rid of it/parting it. I will be keeping this car and restoring/upgrading as things need it/money is available.

I usually do my own oil changes but about once a year I have it done at an independent Subaru shop that is very good with SVXes and have them do a whole check up on the car. I just don't have to knowledge to check everything they can.

So here's where I'm at with my latest checkup:

Valve Cover Gaskets leak oil - medium = $503.00
Front Crankseal and Camseals leak - medium to heavy = $498.52 with Timing Belt

There's a few other things but that's for other threads.

A couple of questions here.

One would be, just fixing the issues listed, are these the types of things that can be done by a smart person via a "how-to" situation. For example, I am not a mechanic and could not even tell you where these parts are, but I have successfully changed spark plugs, fuel filter, and a few other thing based solely on following well documented How-To's posted here.

The other would be, at what point is a "engine rebuild" warranted? What does that even entail? Is an "engine rebuild" basically replacing all the seals (which it seems like I would be halfway there), or is there some other stuff done like machining, etc?

I guess I'm just wondering if I actually had these jobs done, how much farther is it to the status where you can basically say the engine has 0 miles on it?

Sorry for my ignorance.