Your making this really complicated.... You have two paths to take.
You can do the more common path and Top Swap. This requires you to purchase Supercharged 3800 Heads, SC 3800 LIM, Gen X (3 or 5) blower, gasket, fluids, whatever else you end up breaking or needing to replace along the way. You get easy power and can hit the 330 WHP range with Heads, Cam, Exhaust, Intercooler etc.
You can do the least common, yet more fun path. Buy GMR Badass's kit. Its an amazing price. This kit includes everything you need IIRC. Bolt it all on, drive, wait for your transmission to go kaboom, buy a TEP Race trans and live happily ever after in the 200whp-800whp range depending on how crazy you go.
I am currently running a T67 turbo on an l32 motor with an XP cam. Fun as hell to drive. My trans is eating the dust and I can feel it, so I am also currently building my own up. 1in GMR chain, 1200hp GMR Turbine shaft, Precision TQ Converter, TEP Stage 2 rebuild kit... You'll want to do some trans upgrades if you plan on going into the 300whp range depending on the miles on your car and how well it was taken care of/beat on.
Then there is tuning: 3 Options in order of worst idea to best idea
Mail order tune: Need I say much? Someone who hasn't ever seen your car guesses at a close conservative tune and away you go. Wont be the best option but it will work.
Buy HPT and start reading: This is what frosty and I did. Lots of books, time and one engine later we now do all our own tuning...well might I add.
ZZP/Or other reputable speed shop local: Install mods, go to shop, pay man, he tunes car, leave happy.
So select power adder, select tune method, pay people, yay go faster.