Dude,
flick the girly spanner Grab the big shifter and have a go!! Gearbox uses a tapered plug and the steel plug likes to hold on to the alloy housing. I have never had a disaster with these plugs - I personally wouldn't use heat but to each his own. A hint if the box is out of the car ..... lay the box down and use the weight of the box to your advantage. If you have it standing on end, it will easily want to topple and half your effort will be in pushing against yourself to hold it upright.Hope this helps.
Cheers