Thanks, alozzy. You're right, it's a 2012. It's hard to read the nissanpartsdeal.com website to know which part numbers might be backwards compatible. When you say backwards compatible, I assume you mean that more recent displays would probably work? Unfortunately, the nearest I have found to mine so far is a 3NC0C, which shouldn't be too much earlier than mine. But I can't find any that are 3NDxx. (My model was only installed between June and October in 2012.) The dealer I tried to talk to today (about getting the code for a unit if I bought a used one) was not very forthcoming and didn't seem very knowledgeable. I may have to call around dealers and see if I can find anyone who knows.
When you say check the electrical connections, do you mean all the plugs that go into the back of the unit? Goldbrick suggested checking the fuses, but since the display lights up I doubt that could be the problem. It just doesn't respond to touch. The Open/Tilt button doesn't move at all when you push it, which makes me think it was pushed way too hard. The car belonged to a local authority before I got it so it certainly didn't have one careful owner! It has quite a few signs of abuse inside and out, so I think the unit was just mistreated. Anyway, I'll have a go at taking it out and see if there's anything obviously loose, etc. But since the Open/Tilt button seems to be broken, I think it's the whole unit or nothing.