If the rust is just some surface corrosion, that's not bad. If the pusher moves freely and the controller and blowers work, then that price sounds pretty good.
Glass, gaskets, and the grates seem to be easy enough to replace, though I haven't had to do that yet.
When I bought my mag, the first owner ran it in his basement and only brushed the window off once in awhile, so the glass was completely grimed over. I actually just used a good shot or 12 of windex, and a roll of paper towels, and she cleaned up nice enough to light my farmhouse's huge kitchen quite well at night, it's just a little foggy along one edge, but if I take it out I could probably get it even better.
I've also taken the blowers and cleaned the "squirrel cages" with a swab, that made mine run much quieter. Took 15 minutes.
As for thermostat, mine is an "off the shelf" from the local hardware store. Two wires and a wall is all it needs. Hope this helps, I've learned a lot from the good folks on here.