Re: Can you use existing Sirus antenna
Yes, you can reuse the stock Sirius antenna.
Im pretty sure on all '08-'10 models the Sirius unit is built into the stock radio.
This is direct from wkjeeps.com (pages 20-26 on the PDF for '08 + installs):
2008 82210940AB Gen 2.5, Sirius Satellite Radio Installation Kit: includes antenna, wiring harness and I-sheet. Requires radio with integrated satellite radio (RES, REQ, REN or RER). Installation instructions PDF
2015 Altitude - Billet Silver
Tow PKG + Park Sense + Backup Camera + Navigation + Alpine 9 Speaker
Mopar Slush mats + Cargo, Mopar 4" Chrome tips, 1.25" Bora Spacers, 15% Tint,
Overland Black Mesh, Gorilla Black Locking Lugs, Sylvania Ultra H11 Lows & Fogs