i didn't see any connection to overfilling, the Oil change places overfilled mine all the time.
It did however leak one week when it was cold last winter, then it quit all on its own and didn't come back.
yes 553k, that's really good, didn't he say he put a new motor in it at 450k or something. amazing the 1.6 will last that long.
I also read some guys say they have never replaced that seal in 200k + miles....