I've removed these and honestly, it's not worth the effort. You can do a thorough job of cleaning the crud off the base of the case with a little effort, some clean rags and the right chemicals.
I have a set of these. Nothing fancy but works in stuff like this.
Grip 7 pc Super Thin Wrench Set https://www.amazon.com/dp/B001HZQW0Y/ref=cm_sw_r_apan_glt_fabc_GHYXVZ1Q3GEHGWWGH4A3?_encoding=UTF8&psc=1
Also, here are the width of these wrenches so you can see if it might fit.
1-1/4” & 1-1/8" = 0.157"1-1/16" & 1” = 0.160”15/16” & 7/8” = 0.158”3/4” & 13/16” = 0.159”11/16" & 5/8” = 0.118”9/16” & 1/2” = 0.120”7/16" & 3/8” = 0.119"
Also have this. I forget what size ranges. But it comes in handy. https://www.acehardware.com/departments/tools/hand-tools/wrenches/2401248?x429=true&utm_source=google&utm_medium=organic-shopping&utm_campaign=organic-shopping
Yes, you will need to grind down an open end wrench thin enough to fit in that narrow space. As I remember, I believe it takes a 5/8" end wrench. There is also a tiny set scew that you will have to loosen first.
The motor housing is not together properly in the picture of it laying on the bench. You can see it in the picture. The left side has a gap. This is causing a misalignment of the shaft and the bearing.
I use a plastic hammer to tap on the housing to get it to "pop" in.
Hope that helps.