How hard would it to rewire a roof mounted antenna if I shaved my stock one? Is it fairly easy or a total pain in the ***?

Also, if I were to hook up XM, would I need another antenna or can I use that new roof mount one as well for both?

 

If your shaving your stock one, just get a powered one you can put inside the car so you wont see a thing. We sell em for $50 at CC.

Yes, XM needs a separate antenna which will need to be on the trunk lid or roof for the best reception.