The spark plug thread is planted very deep. Since the original thread is already spoilt, you have no choice but to rethread. If you don't solve this problem, your spark plug will "tendang" out from the sparkie slot. As a result it could also damage your spark plug coil pack.
Because it's planted so deep, I think he has to remove the head to do a good job. Therefore you will need new head gasket set. And since the head is out, ask him to replace those valve seals too. You don't want to revisit this 6 months later. It would also be a good time to check and replace the oil separator and 3 pieces of air hose if necessary. Trust me if they have not been replaced, they are probably clog up as much as 60-80%.
What's the offset of your wheels? I notice it's pretty aggressive. The original offset is 47 but my guess those on your wheels could be less than 30. This could also affect your ride.