Just had the spark plugs changed for 60k miles. When I picked up the car, the infotainment screen won’t turn on. Radio still works and bluetooth/USB still work. etc. just no screen. Backup camera doesn’t work either. Climate control is good.

Tried holding down the audio system power button for a few seconds in ACC mode, nothing.

I’ve contacted the mechanic who did the work and he’s not sure what could’ve happened. Didn’t know if the nav screen was connected to the throttle assembly? Mechanic said the battery was never disconnected, but I did notice my average mpg was reset if thats helpful.

Radio fuse is good.

Any ideas what I can do besides taking it to the dealer for an expensive prognosis?

 

Either it is sheer coincidence this happened, or the battery was disconnected.

At this point, you might as well disconnected the battery for 10 minutes (minimum), and see if the display returns again after reconnecting.
Given that your vehicle is a 2014, there is a good possibility the radio head unit has crapped out in terms of giving you a display.

 

Do you think the issue lies with the radio head unit and not the screen? menu/home bottoms still work

 

The screen is controlled by the radio head unit...think of it like a computer monitor for a desktop computer.
How often does a monitor malfunction? Usually never.
In this case many have reported the same issue you're having on 2014 IS's...it's not an uncommon thing unfortunately.
Electrically I don't think we've had a reported screen failure to date. Some of the 2014's did have the screen delaminate...but that's a physical failure, the screen actually still did work even when that happened.