can you reuse the factory antenna on an 06 jetta?

are you talking about xm? or radio ? but I believe the answer is yes on both accounts. Theres a thread here describing xm modding for the adapter plug to work with avic units. For vw if i remember right (as i havent seen a newer vw) theres an adapter for the radio ant. to go to universal tip.... 40vw10 comes to mind for a metra part, but dont quote me please I could and probably am wrong.

yah xm. what about the tuner can that possibly be saved as well?

not tuner, i dont believe. check out the search and I remember reading a gm vehicle i think it was that showed how to mod the ant.