Depending on how old it is:
I agree with at least the front seal: pull the balancer to check and see if it needs to be sleeved, replace the front seal at the same time. I wouldn't necessarily open up the front cover unless you have reason to believe there are other issues, or lots of gunk.
Also while it's out:
1) It's easy to roll it over and check the cam lobes for spalling, check tappets before you roll it over - they sometimes go first.
2) If the engine still has babbit rods, it's easier to adjust them while the engine is out.
3) Check the clutch fork and ball for wear - easier to replace while it's out.
I'm certain more experienced folks will provide more advice.
Have fun!
Bill
