They are standard metric 12spline bits, so the ones you have (from having a T25?) will fit fine.
Once the driveshaft comes off there is just a flange - it's not like those bloody Vauxhall etc gearboxes where the shaft comes out and drops all the gearbox oil.
You will need to undo the 17mm/M10 bolt that goes across the bottom of the upright, to swing this out of the way, enabling you to get the driveshaft out. I sometimes find getting this out is a proper git. Undoing the three M8 bolts that secure the lower ball joint is much easier, but you must make sure it goes back in the position it was in.
Once the shaft is off, you'll find the outer joint knocks off with a few hammer blows, then you can either remove the inner joint and put both over one end, or remove the circlip that secures the inner joint, tap that off and replace the inner boot from the 'right' end.
The outer boot can be done without removing the driveshaft - just swing the upright out of the way and welt the outer joint off - I've done this in the dark with DannyP outside a hotel in Nurburg!