Use heat on only the bolt. Your going to be draining the gear oil anyways. Get the drain plug nice and hot. If you can get it to and orange color, not red hot and then put your wrench on it to loosen it up.
uahh sir, i respectfully request you re-think this statement.
physics states that things that heat up, expand.
expand = increase diameter sizes.(in this case of the plug)
i would, and have done is, using a 10" length breaker bar, 1/2 " drive and a 6 point socket, depending on the bolt, plug, with the correct drive, or allen and try to budge it.
if it does not budge, and or you do not feel comfortable,
i would heat the aluminum with map gas aka propane torch.
oxy/acc is too hot, do not use it.
heat it up for a minute, PB balster it.
heat it up again, then apply wrench when JUST THE ALUMINUM is warm
should come out like butter.
and when you re-install it, anti-sieze
not trying to be a richard head.