How do I change the switch for the dome light?

Can't speak to a Prime directly, but often there's not much to those switches, other than a springy copper piece that slides, and so not much that really can go wrong with them that's very hard to set right. Again, I don't know if that's true in a Prime.

 

In my 1985 Toyota Corolla LE, the upholstery guy fried out/broke the dome lamp when he was changing the roof upholstery which was hanging on my head. He did an excellent job otherwise. I replaced both the lamp/switch assembly and bulb. On that car, it was very easy.

Subscribe to TIS for a day and download the instructions. Is that one of the left/right map-light switches or the dome-light switch that turns on both map lights?

 

Yeah, I subscribed to them a few times and downloaded several sections of the repair manual. The last time I did that was when I removed and reinstalled my rear bumper cover.

 

If you mean the three-position light switch in the map lamp assembly (roof console box assembly), I’m not sure this is available separately as a service part; Figure 81-21, Interior Lamp, lists only the complete assemblies, part number 81208-47200-B0, with telematics (“SOS” button), or 81208-47070-B0, without.

The Repair Manual (more info) covers removal and installation of the assembly, but it’s not difficult. The assembly is secured by four clips, and you use a molding remover—identified in the manual as Toyota 09061-1C340, equivalent to KTC AP201-W (page in Japanese), but any similar tool would do—to pry it out.

Current editions of the Manual recommend precautions against electrostatic discharge (ESD) when handling the assembly, with a wrist strap and anti-static mat grounded to the car. This wasn’t mentioned in earlier editions, so I imagine it was added due to warranty claims experience; an automotive assembly such as this would usually have been designed for ESD immunity.

 

You can repair the old assembly without replacing it with a new one.

 

I just fixed this by following the youtube video with ID# ETv0WX4BsX0 (can't post links sorry) and also squeezed the contacts a little to apply more pressure, and replaced the dielectric grease. For $198 cheaper it's worth a try. If that doesn't work or you don't want to mess with it, I also have a whole map lamp unit I bought off eBay that I won't be using, happy to sell cheaper than anywhere else.