We have also replaced the battery in our 98 ML. Good idea to replace it anyway with winter approaching (if you live in a cold locale).

On the transfer case seal, we had ours replaced under warranty.
A 98 with 39k miles should still be under warranty unless it was
one of the very first off the assembly line in Alabama. We ordered ours in September '97 and received it in May '98.

If you do a search in the archives, there is an old posting from May 18, 2000 which lists all of the part numbers needed to update 98 and 99 ML door seals and weatherstripping to the level of 2000/2001 models. It was posted by Christopher Kowalski.

Also, go get the front sway bar update installed if it wasn't done previously.

Enjoy,

Ken