Unbelievable! So instead of clearing the message he just disconnected it! I guess you’ll need to find a better mechanic. I would still go back to the this guy and complain! He shouldn’t have disconnected it.
You’ll need to get it back working first. If he won’t, you’ll need to get your money back at least. As he could have simply disconnected the fuse or cut the wires which could be quite costly to fix.
As to clearing the perform service message, take a look at this: [https://www.chryslerforum.com/forum/chrysler-voyager-town-country-21/overhead-console-%22perform-service%22-4918/|Overhead Console "Perform Service"]