Maybe this is too late but here are some thoughts on your questions.
1. where is the best place to hang the gear box so it is balanced nicely?
The whole gearbox is pretty cumbersome, and it may be worth thinking about taking the transfer box off first. Depends how much help you have or the access/facilities.
2. I have what seems to be an engine oil leak between the bellhousing and engine what do i need to do to replace whatever is leaking?
Yes, this is the rear engine oil seal, which fits in the alloy rear housing that bolts onto the engine. You need to take off the flywheel to replace this not too expensive but be careful doing it as you can damage the new one putting it on. Make sure the lip faces inwards and is not crinkled as you fit it.
3. do you remove the gbox mounts from the chassie or do you remove the nut running through the rubber on the mount?
If I understand this right, it does not matter. Whichever is easier for you.
4 anything else i should know or do as it will be my first time removing a gearbox and i hope to not have to do it again fo a while!
Well, if it is slipping because of contamination on the clutch and you want to wait for warmer weather, I have a bodge for an oily slipping clutch. I got an oil leak with the bell housing wading pulg in so there was a couple of pints of oil sloshing around n ther and it was slipping a lot, but not worn out.
Fit a piece of thin hose into the drain at the bottom of the bell housing and run in a couple of pints of paraffin/kerosine and run the engine with the clutch wedged down and the car in high 5th (so it will stall if the stick holding the clutch down moves). Leave it for 30 mins or so. Switch off and drain out the sludge. I did this twice and having left the plug out I now get a little drip when it is parked but no slipping and I will do it after the winter.