You can HELI-COIL the saprk plug hole, its routinely done. Like mentioned, you thread a new set of "threads" into the previous hole. usually requires enlarging the current hole. The you plug "bites" into the new metal threads. I would first go back to the shop that made the intake gasket repair and have them access the damages and make them pay/repair the spark plug hole. Do you even know for sure what amount of damage was done, what did the dealer say? And why would you have gone to the dealer and not back to the place that did they original repair, sounds related to me. Definitely look at repairing and not replacing the head!
Mike Skurich
1969 C3 Corvette Coupe
1988 C4 Corvette Coupe
1992 Misubishi 3000GT VR4
1997 BMW F650ST
2001 VehiCROSS
2002 BMW R1100S
2005 C6 Corvette Coupe