$400 installed? Sounds normal to me...
Depends if he has a HU that is XM compatible (has he checked into Sirius too? XM is not the only satellite radio out there [img]smile.gif[/img] )
If he doesn't...i can see $400 installed. Never did one at the shop while i worked there but i did my sirius. Doesn't take too long, just a crap load of wires to run. Don't kink the wires coming off the antenna either or you may damage them.
Hardest part is hiding the wires from the antenna if you choose to put it on the roof of the vehicle. The rubber molding around my backwindow was too old to be pushed back in place so i mounted it to the trunk lid near the window. Ran the wires underneath the trunk lid to the demodulator...no biggie. Reception isn't quite as good as roof mounted, but i can't complain.
but yeah...$400 for parts and install sounds nice, especially considering the warranty you get.