Drill Rebuild/Maintenance?

My drill (an 18v Bosch) has seen a lot of hard use. I’ve noticed that for some time it had slowly oozed grease and more recently the SDS collet/chuck has become a bit sticky. Otherwise everything seems to be functioning fine.

I was wondering if anyone has ever rebuilt their drill or maintained it in any way? I can’t find any manufacturer’s guidelines on this but have stopped short of calling Bosch. Has anyone sent their drill off for routine Mx with good results?

My RH328VC came with a 30ml tube of grease, which is labelled with instruction to apply it to the splines on the drive end of the bits; it is also labelled as inapplicable as gear lube.

Back in the day, I opened up about twenty, 24V Bosch Bulldogs and Annihilators, to modify for remote battery packs. Did some minor rebuilding and cleaning, new carbon brushes, new trigger switch, etc. Cleaning and greasing the SDS chuck was routine maintenance. 

Bosch always had parts schematics available, and parts were readily available.  https://www.boschtools.com/us/en/service/manuals-and-part-diagrams/

Have you searched YouTube videos? That is my go-to for any unfamiliar repair project. https://www.youtube.com/results?search_query=Bosch+GBH18V+repair