Got a Sirius car kit for xmas. got a few questions about it?

Im curious, anyone have any problems with it? its the Sportster 4 unit. mainly stuff like, should i have it professionaly installed, does the actual antannae go on the outside or the inside of my car cause im worried about going thru a carwash with it and having it get ripped off, stuff like that, getting it wet, etc. and how many stations do you get with a basic subscription, and is it worth it?