This evening I cleaned up the bellhousing which was covered in a layer of gearbox oil and grit. Once I had cleaned off the cack, I removed the clutch release bearing support (three nuts) and dug out the old seal. This took a bit of brute force my special rear brake drum removal tool. Once out it took a few minutes to put the new seal in place. I put a thin layer of high temperature gasket seal round the outside of the seal where it makes contact with the bellhousing. I smeared some oil on the input shaft, pushed the seal into place, tapping it with a drift to get it seated properly.
I checked the tightness of the bellhousing nuts while I was there, and was able to get a half turn on all of them without using excessive force. I will check the manual for a torque wrench setting tomorrow and tighten them to the correct torque.