I would think that a good mechanic can R&R a 603 head in 9 hours. Figure another $250 for parts and miscellaneous BS (while you are at it). If you decide to do a valve job while the head is removed, figure another $300-$400.

But, if the head is cracked, you now must find another one. You could probably get another #14 head reasonably cheap ($300 or so), but, if you need to bite the bullet and get a new #22 head, you are looking at another $1200 or so. Could be more than this now. You would need to add some cost to transferring all the valves/prechambers/hardware, etc. to the new head.