I've got a whirlpool tub that has not worked since I moved into the house. When pushing the switch, I can hear the "groan/hum" of an electric motor that is not turning.

One problem is that I don't even know for sure where the panel to access the motor is. The panel is covered over by the troweled wall texture and painted over. I am not sure if the panel is on the long side of the tub, or the end, and I would rather not rip off the texture until I know where it is.

Any insight on what might be wrong with the pump/motor, or how to gain access to the panel?

Typically, access is on the long side of the tub, and the home builder leaves some way to get in without tearing stuff up. Not always the case though...

The texture was applied by a really stupid previous owner, not the builder. I had to chisel out an electric outlet he partially covered up in another room. You're right - if I thought the builder did this, I probably would not have bought the house for fear of what else might have been done!

Will it work to get a razor blade and try to cut and peel the texture off the panel?

Probably the capacitor is out on the pump motor, that will make them hum but not start. Fairly simple & inexpensive replacement to see if you can get it working again. That is if you can find the pump, We had one and the access panel was on the end and in the bedroom next to the bathroom.

How about the old water glass "stethoscope" trick around the tub while someone else operates the switch to isolate the location?