Also make sure you completely remove all of the old seal. They rip and a metal ring can get stuck in there which will cause the new one some issues.

 

You can check the flange when you remove it. If it's not grooved or damaged on the surface that fits in the seal shaft area there's no need to replace it. Yeah, it's somewhat of a pain to do it again if you find it's grooved and can't leave the Rover out of service until you replace it and so have to remove the propshaft again, but not a huge deal. You only have to remove the diff end of the propshaft and if you've just done it, it's pretty easy. At only 103,000 miles the flange shouldn't be grooved.
If you don't need to replace it, you can put the money towards a torque wrench, which you should have anyway, if for nothing else then to torque your lug nuts correctly.

You might check at an autoparts store to see if they loan/rent torque wrenches. Or ask friends.

 

Or put the money toward a new serviceable front drive shaft.

 

Nice! I just realized that a torque wrench isn't only the tool that is hooked up to an air compressor that they put F1 wheels on with in the pit... I will pick one up at Harbor Freight for $25. Woohoo!