10-4 on the electrical, although if you want it 'legal' the inspector will want it to be hard wired, that is to say wired with flex and wire nuts, not plugged in.
18ga wire is fine for t-stat, run 3 wires if you want seperate fan only operation.
I have a 1000sq ft, and the 75K mr heater works quite nicely. My dad has a hot dawg and i think the mr heater fan is quieter. I was expecting some noise, but i was pleasantly suprised.
I watched northern tool every week for like 3 months, finally it went down further than the usuall sale price and i jumped on it. dont get the flue kit online, its over priced. I hung the unit and wired the t-stat, but my electrician ( who was wireing the whole garage) did the high volt. I also dug my own trench and had the hvac guys run gas line and cut the flue. Everything was inspected. Also had to upgrade to slightly larger gas meter (free).
I used a RiteTemp programmable tstat from home depot because it goes down to 35 and others only go to 40-45, with out getting somthing special. I keep it 35-40 when im not in there and crank it up to 60-65 when i am. Heats fast and i dont cook when i stand infront of it.
The walls are r-13 and i have about a foot of cellulose in the attic, which really helps with retention. I have never caught the thing running when i get home and its 0 outside.
dont mount the t-stat on an outside wall (sometimes kinda hard i know) or right in the vent of the heater or it will never work right.
I need to share the pics though, ill take some tomarrow hopefully.