Manual Transmission - Clutch Help / Transmission Build

Hey guys,

I picked up a cheap 99 ls1 trans am that the clutch is slipping in. I'm going to order a clutch and the parts I need to fix it up this week. My plans are to build an engine similar to this one listed below.

http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&vxp=mtr&item=180866638338

This car will just be used as a fun driver, not everyday. But when I have the tranny pulled, what should I have them all do to it? My plans were a Level 3 Monster clutch but beyond that I dont know the weak points.

Also is that the clutch for the car? And is there a good vendor to get it from?
The car is just gonna be a burnout/beattheshitoutofit/but will probably get quite a few miles on it.
The car is bone stock and only has 70k miles. An older dude had it for the majority of the time.
And is now the time to do the headers/y-pipe/etc too?

Sorry about the multitude of questions but I just want it built right the first time.

Thanks!!
Cody

If it has higher miles and you've no history of the trans., it might be a good time to go through it, just to address the basics of the parts, check endplay and know what's worn.