Gaylord is probably the closest town with dealers.
A little Google-fu found Wolverine Power Systems in Gaylord (.
https://g.co/kgs/1MCFN5 ) was a Generac dealer. Haven't dealt with them.
Cummins Bridgeway in Gaylord (
https://g.co/kgs/4GwrTH) service any make/model of generator, but they probably only sell Cummins. Might look at them to compare prices. I've dealt with their office just a little at work. They seem OK. They will drive north of the bridge, so Alpena is definitely in their range.
One thing to keep in mind with propane is to have enough vapor pressure/boil off in below zero temps to keep everything running. I've seen a 50kw generator choke out a commercial water heater when it revved up to handle an increased load on a really cold night. Once we added a second 1000 gallon tank we haven't had any more problems. Your propane supplier could probably help you calculate the tank size you need using your total BTU draw. 500 gallons might cover a homeowners needs. 1000 gallons would definitely be more than enough.