I'm in Plymouth and I used Centerpoint Energy (Gas company) to replace my furnace and change my electric water heater to a gas one last May. They subbed the actual install to River City (in coon rapids?). They did a pretty good job and did both in the same day.
Center point was one of the only ones that both returned my initial phone call and actually gave me a bid after meeting with me, taking the measurements, etc and finding out what I needed.
There is one that a couple friends have used (and really liked). I had them come out and give me an estimate. After spending hours taking all the info, he never called back or mailed me the estimate like he promised. After they sent me a survey to see if I had bought one yet and to rate the salesman, I had to explain why they could go f' off. If they didn't send a bid, they couldn't be chosen. (And I bought one of the two stage burner, variable speed fan units with an air conditioner at the same time, so it's not like it was cheap unit) He said they had fired that particular salesman. I wouldn't personally recommend them, but several friends did and would. I won't post their name, but will tell you if you want via IM.