There is a place that sells the navigation unit and a kit to make it all work right with sync and all that but it is upwards of $2500. I have also wanted to get one to replace my factory radio and after the price II don't really care to do it.
Yup if you have a 09+ you need a unit from a 09+ truck 08 navs are totally different hardware wise. 09 is when Ford started to add sync to the trucks and changed a few things.