Basically, a strong motor with full 3" exhaust, intake, and ~14 psi (you will need a way to raise/elimnate fuel cut) should get you close. An lightweight crank pulley (not reccommended) or electric fans will help get you closer.
Full 3" exhaust from the turbo elbow and back.
Intake..ur choice, most people like K&N
Boost controller...electronic or manual, whatever.
Intercooler hardpipes...preferably 2.5"
Bigger thicker intercooler..like spearco or whatever.
bigger better fuel pump
set boost atl ike 16 psi
Depends on your goals, spare cash, and availability.
If you really are going to quit at 300whp, stock parts should suffice quite nicely. If you get the bug and end up with a 500+ whp monster, you'll be bitter that you didn't replace a whole lot more of the internals while you had it apart the first time...
Seriously tho, the headgasket is the only serious deficiency in the 7M. Fix that and you're set.
Sites... that's a tough question. Personally, I almost always pick up my parts locally, but I live in a big city with a lot of import stuff available pretty easily. Perhaps someone else will chime in here.