Toro 20322 Personal Pace RWD transmission

I have a 20322 Personal Pace mower I got for $70. So far I've fixed the handle, swapped the carb and air cleaner (with prime bulb and spring governor) from an old Craftsman and replaced the drive belt. It works well but there are some crunching sounds from the right rear wheel when reversing. I ordered new rear wheel bearings because some people have said that those can affect how the gears in the rear wheels align with the pinion gears.

The mower is an odd combination of great and bad design features. The engine is much better than the rest of the mower, there's way too many plastic parts that break and I don't know why it needs to weigh so much.

Two questions:

1) I've read that Home Depot sells rear wheels that have metal gears that are cheaper (around $18) than the older plastic geared wheels I have, and that you need to swap the pinion drive gears with later models if you go to those wheels. Has anybody done that?

2) I tried to open the transmission case on my mower to check the grease. I removed all the screws that hold the case together but the case didn't want to come apart. I tried wedging a flat tip screwdriver in there but stopped when it looked like I might damage the case. Does anybody know how the transmission case comes apart?

Thanks