Navigation Removal Info

[BoostedA4203]

Im looking to remove my factory 4:3 navigation and replace it with a pioneer avicf90bt but have some concerns about how it will affect my on board computer...i have taken the nav out and can still cycle through the cluster dusplay using the blinker stalk so i am wondering if i will only lose the ability to recalcute gas mi, speed, time, etc or will it stop functioning all together. Also i know the navigation unit only serves as a disply and that everything is ran from the navigation disc drive mountd in the trunk so i am wondering what harnesses i need and what exactly i have to do to hook up the aftermarket radio in place of the factory one..any help would be great!