It's not difficult. You need the gearbox, gearbox mount, starter motor, clutch/flywheel, gear linkage and clutch slave cylinder pipe.
The 6speed Getrag gearbox is a bulletproof unit. Never heard of one breaking, so little need to recondition it. They can be picked up secondhand on eBay or from breakers for £400. You should be able to get all the parts needed for £800 - 900 and the breakers will buy your old box back off you.
I did mine myself in 8 hours and I'd never even done an oil change before that.