youtubing,
the procedure seems straightforward, if a bit laborious.
and looking at the comments below the video, a number complain that the leak recurs soon after, again.

my guess is,
if the shaft wobbles (from wear and tear), no amount of oil seal replacement will result in long-term cure.
but the trouble is, one won't know that, unless one tries it out first and/or has the shaft examined at a machine shop, once dis-assembled.

good luck, sir.