Looking for guidance on removing shell on K-line Plymouth switcher

I am looking for guidance on removing shell on K-line Plymouth switcher. I think it will be pretty straight-forward, but a couple of questions. From underneath I see:

6 screws (4 in back, 2 in front)

2 screws (SMK toggle switch)

2 screws (REV toggle switch)

4 screws (at the outer corners of the black chassis)

4 screws (on top of black chassis - near rollers)

I'm wondering if there are any of these screws that I don't need to mess with to pull the shell off.

Do I need to remove the front/back bumpers (so the couplers have clearance)? It looks like I do.

Thanks.