After overheating there is a code P0306, shakes, little noise from underneath, no check engine light on dashboard

Eight months ago it overheated, I replaced the thermostat, coolant, and radiator didn’t really work, took it to a shop because a “check engine” light turned on. Turned out to be a P0306 and had a blown head gasket, engine was good this was at 117,564 miles but the mechanic suggested to have the motor replaced instead of just the gasket since the price was about the same. We put a Bluedevil sealant from AutoZone and worked fine until last week at 125,685 miles the engine just began give some small shakes with a tapping noise from underneath. It powers on instantly and drives front and back, just replaced the coils and spark plugs too but it has no check engine light on and the car scanner tool reads the same code P0306 One thing I noticed was the fan felt like it gets stuck when turning the ignition on, it’s not always but has done it 2-3 times since it overheated. Is it worth fixing it? I really love my truck. :(