I know it's on a previous thread that the gearbox filler is on the side but is it drivers side with a plug that needs a 1/2" square socket to undo it? Also and tip on how to undo it if it's very tight as access is tight and can't quite get the socket in all the way.

I use a 1/2" knuckle bar about 18" long I think?

 

It's a taper thread so it needs a big heave-ho to crack it off initially, then it comes out very easy.