Welcome to GenVibe! Sounds like you got a great score!
As far as the radio reception, sounds like the antenna amplifier is bad. The amp is located in the antenna base and you have to remove it and replace it with the same, maybe from a junkyard. You drop the headliner a bit at the rear hatch and then get a 21mm socket to loosen the nut, then it comes off. Here's a replacement part I found on ebay so you know what it looks like:
http://www.ebay.com/itm/16-Aerial-Anten ... 2188673338
As for XM radio, you should be able to tune to XM channel 0 and get your radio ID, then sign up for a free trial of XM. Just call them and tell them you are a new owner and want a trial.
The OEM radio design is from 15 years ago so it doesn't have any modern features or even an aux jack.