No worries, i'm not really sure on prices tbh. A large part depends on if you are removing the head yourself, or paying the engine
shop to do it?
Either was make sure you get a reputable place to do it though. There are countless 'rip off' engine places, where they will wreck your motor fitting some **** head they found in a scrapyard somewhere.
As for the secondary air, it only works during start/warm up, so it won't be related imo.