Alot of good info about swaps floating around. Here are just a few good sources of info..
VT951's Build
Basic 944V8 Swap Info
Texas Performance Concepts
and a good forum at..
Home
The big stuff that most cant just do in a garage themselves needed are mainly the uprights (engine mounts), bell housing adapter, headers and obviously the rest of the exhaust. Regarding the headers, there are off the shelf parts available from Jegs/Summit..etc that fit, but the passenger side needs to be modified a pretty fair amount in order to clear the steering shaft.
A buddy of mine will be doing an LS1 swap over the winter, we are hoping to have it done by spring of next year.