if you take it to a shop they will grind the head in the area where the crack is down till the crack is removed. Then they will proceed to weld new material in. The important thing to do is when you get the head back to go ahead and put new valve guides and new seats in there as the amount of heat will 100% distort the area around the ports and so forth. If you plan to have this head repaired go ahead and buy 4 new seats and guides and get it done right. You having the head just welded and not getting the rest done is the same as giving him the head with the crack in it. You don't have to get a valve job done but I would certainly have the core parts replaced. Then you can get a good amount for the set.
