Tell me the easiest way to do this. Can I use parts from other GM's or do I need to go aftermarket?

It is very easy; the hardest part is rounding up the various parts to do the job. You can use all GM parts for an A body, use GM parts for larger brakes or go aftermarket. I prefer to use the original stuff. To start your education on this topic (which has covered here many times), go to the lower right hand part of this page and look at the drop-down menu that says "Hop To". Scroll down to "disk brake conversions". Once you have digested that , then any remaining questions you have can be handled here for sure.

Thanks JWagner.