I have done mine. I was able to remove everything with a drift and visegrips. I installed the seal by pushing it into the upper groove by hand and gently tapping till it was home. If I remember correctly it looked a bit tight for a Chinese handcuff type of seal puller. It was not a difficult job, just upside down and oily as mentioned. I wish I had done what Brute said. I did use some carefully placed sealant. Mine still leaks a bit. I do run synthetic though. My future fix is a rebuilt replacement swap. I don't want to do the seal again.
If it is not a bad leak I would leave it. Unless your bored.
Liz, covid, murdered 10/19/21