the 300 tdi flywheel is fine - its just the housing i swapped to make it go into the gearbox.
The existing tdi housing will fit, you jus gotta miss out a couple of studs.
Fitting the top linkage looks to be a gearbox in pieces job - stick with yours i would say.
Mine has both disco axles fitted, they will be 24 spine diffs which means less free play, and, depending on who you ask, a wee bit stronger.
Also means you get disc brakes, and both my axles were a bit past it anyway.