Issue with electric starter on x485

Long time lurker, first time poster. I have a JD x485 that I purchased used from a reputable private seller (he is known in my area for buying and reconditioning high-end lawn and small tractors). I purchased it in 2015 with about 700 hours on it and have about 1000 now. I know my way around small engines and do all of the routine maintenance on it myself and I have never had an issue with it... until now. I have 2 acres to mow and I did half of it last night then quit when it was getting dark. I shut the tractor off in the driveway and hopped off to move some stuff I left in the bay it normally sits in but when I went to restart it, nothing. I was hot and tired so I left it sit in the driveway overnight until this afternoon when I went to hop back on it to finish and it won't start. I can hear the starter motor spinning up (like an electronic whine) but the engine is not turning over. I verified it was the starter motor I heard by removing the return wire from the starter and turning the key - no sound. This tells me that I don't have a weird safety system issue since the electric starter is attempting to turn over the engine.

Looking at how the starter attaches to the side of the motor, I can't figure out how I can get the plastic shroud off the front so I can see if either the shaft or gear is damaged on the starter (which would explain why the engine is not turning over). So a few questions:

1. Should I unbolt the starter assembly from the engine to inspect the shaft and gear for damage? I'm not sure if this is easier / harder than removing the protective shroud.
2. If the shaft / gear are damaged, is it possible to just replace them without buying a whole new starter assembly? I had an older Sears DG6500 lawn tractor for many, many years that i had to replace the starter motor a couple of times. The first time, I was able to just buy a new shaft / gear assembly then replace it myself but use the same motor. After the first time though, I couldn't get that shaft / gear part anymore and had to buy an entire new motor assembly.

Thanks for any insight on this issue!