The turbo setup will give your buddy more power than the 3.5L. Here are a couple turbo kits available for the 3.0L. These kits are only recommended with a 5spd, due to the automatics not being able to handle the increased power.
http://www.turbo-kits.com/maxima_turbo_kits.html
I haven't heard of anyone swapping the 3.5 from the 04-05, but there have been some people that use the 3.5L friom the 02-03. You will need the ECU and the wiring harness to be able to make everything work.
I kind of doubt that the interior would fit, but I'm not 100% sure on that one.
Have you uncle check the shifter mechanism (in the center console) to make sure nothing is interfering with it. Also check the shifting mechanism on the front lower side of the transmission next to the radiator and trace it back as far as he can to make sure nothing is binding the cable.