it's "easy" enough IF you take care and use some cable ties to hold it all together when you reassemble it AND weld that socket together AND have a bit of luck putting reverse gear back in again AND don't piss the syncros out all over the place when you remove them

but if you fail, make sure you can get it and all the bits to a local gearbox place to stick back together again

do you know if you have stripped the main shaft of the countershaft gear in 3rd?