If you do not have any idea about the price, then you probably will not install it yourself.
You can add Sirius/XM to almost any aftermarket headunit. As stated above, it is all depends on your budget. Headunit will range anywhere from $100 for the single DIN unit to couple thousands dollars for the hi-end Double DIN DVD/Harddrive Navigation unit with backup camera, BT, IPod Controls, etc. Kit to install is about $40-$50 (Harnes and Faceplate). Many fellow members have very good experience with various Pioneer models. I would suggest to go to the local Car Audio place and see what they recommend. Please, do not go to the BestBuy.
BTW if you upgrade your headunit, you probably would want to replace your stock speakers to really feel the difference.
CUBE