I had someone who claimed to be mecp touch my 91 ls400 and he couldn't install the deck right so I said forget it,and was planning to go to a pro shop, but I just noticed my inside lights, power door locks,power tilt steering doesn't work, and the dash resets itself, the radio, clock, etc.. Maybe he snipped a wire or pulled out a relay/fuse? If anyone might know please help me save $100 that the shop wants. And that's before they install the deck. Thanks everyone

He more than likely blew a fuse. How often does the dash reset?

***EDIT***
I just looked at the 1991 Lexus LS400s fusebox diagrams. Check the #9 fuse, located in the driver's side kickpanel (picture below). It is a 15A mini-blade style fuse.

Here's a quick excerpt from the manual which I read about what the fuse controls. It sounds pretty close to the symptoms which you're experiencing. Try replacing this fuse first and then post your results (i.e. "problem solved" or "these symptoms remain"). Good luck!