Deere 318, what to do while the engine's out

Pulled my engine to replace the starter. I figured while it was out I'd check to see if there was any other maintenance stuff I could do before putting it back in.

I remember seeing a post on firewall insulation, but can't find a kit anywhere. Can someone tell me how to do this? foam insulation from HD work?

Shimming the starter. Old starter had no shims, the teeth on the starter looked fair, teeth on the flywheel had a very small amount of chipping on the teeth side facing the starter. Can someone explain the process for this?

Already have a starter improvement kit, the starter itself just died(tested it dead on the bench). Any other simple/quick/easy things I can do while I have the tractor torn down this far?

Thanks!