Help! - Engine stalling and dying

Hi guys. I just picked up my 00 xj after getting a new head installed, among other things. The mechanic (trusted friend) drove the jeep for a week back and forth to work to make sure everything was set. Yesterday I spent the day removing the interior, cleaning and installing leather power seats. Took the jeep down to get gas today and on the way back it started running rough and stalling when I came to a stop sign. Started it back up and limped home with the check engine light on. Also noticed that the turn signals arent working (they replaced the flasher) but the hazards tdo.

Also getting a ticking noise coming from the valve cover...please help!