Yes the drive shaft has to come out, when you do this most of the gear box oil also comes out, but that's the least of the problems as usually when the seal on the ib5 box goes it's because the diff bearing is on the way out.
Remove bottom ball joint on the osf remove the track rod end.Undo the driveshaft hub nut.Remove the 2 13mm nuts on the driveshaft bearing carrier.Slide the shaft out of the box.Remove seal and replace.Top gearbox oil up.