Welcome to NICO!
First, congrats on your recent purchase! The G35 is a really great car and Infiniti dealers are much easier to deal with than others.
Next, according to Edmunds, you stole the car!!
http://www.edmunds.com/used/20...esult
I don't know the options you have, but with AUTO and a premium package, you should have paid around $15,800 for the car. (that's using the "clean" option)
Don't worry about the driver's side window motor...it's a common problem. The next most common problem is the stereo head deck. The oil problem is more of an issue with the 05-07 6MT coupes and the 05-06 6MT sedans.
So, I think you got a great car at a great price!
Do you have any plans on mods? Post up some pics!!