I've done a decent amount of work on my cars (headers on a GM, 2 supercharger installs, IC installs, nitrous installs, heads, cam, etc etc) and I honestly think that installing Pacesetter shorties on my '05 GT was one of the most pain in the ass jobs I've ever done. Admittedly, I'm not the best mechanic in the world, but still. LOL
Even with the motor mount removed, the passenger side just seemed like a real bitch to work with - I had trouble getting to the lower passenger side header bolts and it was even a bitch getting the motor mount bolted back on if I remember.
I ended up slicing my hand open and needed 4 stitches during the install, too. LOL
I'd say it took me a solid 6 hours of work.
I'd still do it again though. Actually, I'd skip the shorties and just do long tubes. But I wouldn't pay a shop or anyone else to do it...all the pride I have in the car is due to me doing my own work and I hate dealing with shops.