A tech would just replace the trip computer if it is faulty, I agree with that. There is nothing much you can do to them in the shop. An individual with time and patience could possibly make it work correctly again, if the individual has an electrical engineering degree or something like that.
It would be better to explore what is going on with these unrelated systems, especially if the symptoms all appear at once.
One guess would be an ignition switch not providing power to the circuits when it should.

Gilly