Hello Joe,
Are you intending to do this job yourself? If you are, you first need to confirm that it is actually a driveshaft seal that is the issue. I would not characterise this as an easy repair for DIYing, so you would need to ensure you have all the necessary equipment and experience to do this yourself.
If you intend to get a garage to do it, then I would work on the principle of ‘ I have an undetected oil leak that aI need eliminating - can you first locate it and give my a cost to rectify it’?
Kind regards,
Gareth.