Question:
You say the macerator won't run...does that mean the motor isn't running at all? Or simply that the motor runs, but it's not pulling anything out of the tank?
If the motor doesn't run, it's not getting any power...which means the problem isn't in the macerator itself, but in the wiring--a blown fuse... a disconnected wire...corroded connection...or may something as simple as the breaker isn't on.
If the motor runs, but the macerator doesn't move anything through it, it prob'ly needs a new impeller. But as for how to access it to remove it to replace the impeller, your friend needs to ask Hunter...'cuz they installed it.
Once he's able to get to it to remove it he needs to relocate it to more accessible location...'cuz whether or not his current problem is wiring or something wrong the macerator itself or not, sooner or later he will need access to it to service.