2013 chevy equinox oil slude and P0446 vent control circuit malfunction

Hello, i recently bought a used 2013 Equinox with 105k. I had a certified Chevy mechanic run the VIN after i purchased it to check the recalls, and he uncovered some untold stories about the car after the purchase. He informed me the cylinder head was replaced around 95k miles, which he thought was odd for a car that new. After doing some digging I found a service history on carfax that informed me the oil changes were put off way to long in this car (about 15k miles on one oil change) and they were done at dealerships. The filter wasn't completely packed full of sludge but it had flakes of build up in the bottom of the filter feed... Also driving to work the other day I had the check engine light come on for a P0446 Evaporative Emission Cntrl system vent control circuit... I guess my question is should I be concerned about the cylinder head being replaced, and should i do an engine flush for the build up inside the engine... I noticed oil built up in the PCV valve too when i had the cover off the engine. I changed the oiI myself using mobile 1 full synthetic and plan on pulling the filter after 1500 miles to see whats really in there.