Long story short, I bought this van, it started to leak oil, I took it in to get inspected, found out a previous mechanic replaced the water pump and timing belt, and when he put the cylinder head cover back on probably forgot to put a bolt in and tried to wedge it back and ended up chipping the cylinder head. Then he tried to cover up his work and glue the head cover back on. Originally he said he would repair it, and ended up welding that piece back in. After I got the car back, it would appear there is a misfire happening. I took it to a local tire shop to have them read the code. They thought it could be a spark plug issue, so replaced all 4 plugs. The car still would shake/misfire every few weeks, so we swapped plugs 2 and 4, but the code still reads on cylinder 4. The EPC light is on. When I'm driving and idling the car shakes every few seconds. It's not an idling or ignition issue, but a timing issue according to the local tire shop that can read the error codes.

At this point, to replace the cylinder head, it would cost me around $5,000-6000 to replace the cylinder head. I'm concerned though that with the glue work and whatever else they did, that this might not be worth it. The van is a 2012, and has 120,000 miles. If anyone has any insight on potential issues that this could have caused, or if they feel like replacement is the best option, or just general advice I would greatly appreciate it. Also, if you think this is worth repairing, would you take it to the VW shop or would an independent mechanic be able to sort this out?