Hi guys, after replacing my driveshaft seals I discovered that the oil was actually coming from the speedo gear and leaking down.. (No need to comment on that one lol)

I've tried pulling the speedo gear out of the gearbox (prick of a spot to get to) so I can put a new o-ring on it but I can only get it to come out a couple mm and it won't come out any further, even if I turn it around it won't come out any further..
Do I just need to be more forceful or am I missing something?

once the 10mm bolt is removed it should just pop up and out

Yes, it should, but if the "O" ring is stuffed or shredded you may need to apply some force to get it out. Look for bits of "O" ring left behind, it was probably damaged by the last person to visit that part of your gearbox.

At least you found the cause of the leak!

Cool, thanks, I just didn't want to break anything by forcing it.
Is it just a rubber o-ring? meaning I can just get one the same size from an auto shop?