Unless you know electricity inside out, forget about building your own electric heater. You can cheaply buy a good UL listed heater that won't burn down your building.
Are you thinking to run the heater off the generator? Not a good idea. That generator would run a 5000 watt heater at almost full load. If it burns 3 gallons every 14 hours, the math says, 3 gallon x $4.00 a gallon for diesel = $12 for 14 hours, or almost $1 an hour.
I don't know what you pay for electricity there, but here a 5000 watt heater costs me about 35 cents an hour plugged into the wall.
