Gauges not working

I'm thinking of buying a 2005 Buick Rainier from a co-worker of mine for my wife. It only has 122k 6cylinder.:runaround: I test drove it and it feels very comfortable and quiet. Couldn't even hear the engine while in park. Three problems: speedometer not working, fuel gauge not working and the check engine light is on. I read on another car forum site that it is common with this suv. What should i look for considering fixing these problems before buying it and would it be very expensive to do so?:confused: