If you don't have wrenches yet, buy the Harbor Freight adjustable wrench, the big one, as described above.
After soaking and soaking again with "weasel-piss" or equivalent and doing this 10 + times, remove the return hose to the Tank first. Then the Feed line from the motor.
Once these are loose, start taking down the entire system along the rockers & front fender until it gives you enough room to have access to the thermostat. Have a helper hold the thermostat while you use your wrenches to loosen & remove the hoses.
If they still won't budge, take a dremel and cut the nuts diagonally as described above. Do this so you can spread the halves of the nut apart.
The threads do not make the seal so if damaged slightly it won't matter. The Ball surface of the Female hose fitting and the Cone surface of the thermostat make the seal.
And yes, anti-seize the threads when assembling.
Good luck.
Len