That grey head looks so nice and clean. How many hours are on it? I'm coming up on 300 hours this year and may follow your lead. I really appreciate the tear down pics. I noticed the EGT locations look to be possibly too close to the manifold flange. See: http://www.ultralightnews.ca/exhaustsystems/egt_probelocation.htm It would be a good time to measure them and remedy if you think it’s worthwhile.
No real secrets. You need to take off the cover after draining the gear oil to get to 4 of the 8 mounting bolts holding the gearbox to engine. Taking off the rubber donut is straight forward. Reinstalling it on the next engine reqires a compression clamp to line up the holes. Plan on purchasing a new cover gasket. I get mine from JBM Indusries. http://jbmindustries.com
For a shop installation, some use refrigerated air dryers. A cheapo is available from HF https://www.harborfreight.com/compressed-air-dryer-40211.html Still, $400 and only worth it if you do a lot of blasting and painting. Garage Journal has a number of compressor/ dryer threads with some decent homebrew solutions.