Check this thread for installation pics and several suggestions.

http://www.audizine.com/forum/showth...arket-Nav-Unit

1) I've had an aftermarket deck for three years no electrical problems, in general if you do properly install on an aftermarket deck there should be no problems.

2)Yes and no, depends on your specific setup and headunit. Speakers shouldn't be a problem but depending on what you want to do you will probably have to bypass the stock amp

3)you need a double din installation kit but that's it besides basic tools. Any wiring adapter needed will be provided with your head unit then you just splice

4)Nope

5)I have personally had a good experience with my pioneer double din (AVH series) and it meets you requirements. If you can grab an alpine I would, but my last experience with alpine was a decade ago. I heard alpine decks got worse and then better...I dunno do some research on crutchfield.com

6)Look at the pics in the other thread and you can see what most double dins look like installed, the other option is RNS-E from audi