Just time consuming. I don't have diagrams, but it's really not that difficult. Depending on where you split the intake from the heads will depend on which gaskets you will need to replace. I chose to leave the injector rails in position on the lower stubs and just remove the upper half. Remove the throttle body (mark the throttle cable and cruise control cable before you remove the locking nuts. Remove the 6 or 7 bolts holding it to the manifold and remove it. Remove the vacuum lines (probably a good idea to replace them, they'll all be brittle and will break when you bend them), and unclip the fuel lines and electrical connections. Pull the upper manifold and flip it over to access the PCV. It wouyld be a good time to really clean the throttle body front and back and into the intake cavity as well. Add new gaskets, reconnect everything you previously removed, and torque bolts to taste
Take a look at the parts diagram at the subaruparts website for some exploded views.
http://www.subaruparts.com/diag/?mod...ategory=050-A2
Have fun in your garage (Griot's Garae tag line, but I like it!)
Todd