Replaced Coolant Outlet

[PEAC4394]

Hey folks. Newbie here. I recently had to replace my coolant/water outlet on my 2012 Fusion 2.5l and refill the coolant. I burped and bled the system using the bleeder valve and this has seemingly fixed my overheat issue. It only ran hot for a few seconds before I pulled over. Luckily I was directly across the street from my mechanic. My concern is that my mechanic is of the older generation and didn't bleed the system completely. I drove it about a quarter of a mile home with the temp gauge in the normal range. I finished bleeding the air out of the system and my heat returned at the vents and the AC blew cold. The gauge is now dead center and the car is running fine. I don't have anymore air bubbles coming out of the bleeder valve and the reservoir is topped off and maintaining at a steady level. I had a misfire code which now has me concerned. Do note that while the mechanic was "burping" that system it did have a few misfires. He wasn't using the bleeder valve. Could this have caused damage to my head? Again, it now runs smoothly and has no noticeable loss of power. Oil isn't milky. No smoke from tailpipe. Nothing else to indicate a problem, aside from the engine light. When I pulled the code, it was a misfire code and it reset after a drive cycle. Do you think it was a code from the initial event or is there something more sinister going on with my ride? She has 176,000 hwy miles but has never given me a lick of trouble. This is the first time. The gasket on the coolant outlet failed and allowed coolant to leak from around the unit itself.