Is your car a vert? Longtubes won't fit on a vert I have been told due to mid-pipe fitment...
If not, longtubes are pretty straightforward. I installed a set of summit racing longtubes on my 75' camaro. Quite a bit more room under the hood but I'm sure it couldn't be that hard..
1998 GT - CAI, trickflow intake, 3.55 gears, O/R x-pipe, flowmasters, short throw shifter. 145k miles
1995 GT vert - 1 of 36 5.0 Appx. 450,000~ factory motor miles *totaled/parts car* RIP..