When they tell you all the functions of the unit will be made available, I am assuming that means the voice function will work, the little speed graphics will work (that is where you can see the little gages pop up on screen), etc...

Basically what they are telling you is that the unit will work as it says it should according to you owners manual. Make sure if you do have this shop install it, that they go over everything with you so you have a comfort feeling before and after the job is done.

I don't know anything about installs either, I just know that I trusted the guy that did it based on my past relationship with him, and his knowledge. Are you comfortable with the shop you are going to?