While driving the brakes locked up and will not release?

While driving (it's my mother's car and she was driving), the brakes suddenly locked up, bringing the car to stop and won't release. I tried disconnecting and reconnecting the battery and fuses to hopefully reset the electronics, but it didn't help.

This happened a few weeks ago and my mother took it to get checked out. Supposedly it's the ABS module.

What I'm looking for,
How can I confirm it is the ABS module that's bad?
If it is the ABS module, what do I need to know to fix it?

Notes,
My mother and I are complete amateurs. We replaced my alternator (didn't need to move anything out of the way though) and replaced spark plugs, and that's the sum of our experience.
Also, we are homeless, living out of our cars, so we don't have common resources like garages, driveways, 120v power sockets, etc.

We are willing to try replacing it ourselves but working with fluids is a step up from what we've done before, and we've never worked on brakes in any capacity either. Thus, I don't want to be blindsided by something from our inexperience.

Also note, we are literally broke. I'm driving uber eats just make enough money for gas and food each day, and not doing a good job of keeping up. So, buying a bunch of expensive tools or gear is not much of an option, though we thankfully have a socket set and a few other basic tools.