Cylinder Head Question

What the mechanic wiggled was the valve and valve spring. 4 mm seems like an excessive amount of wiggle. 1W&CGuy has made a good call IMO. Valve seals can be installed with the head on the block. I've never seen anyone replace guides without removing the head.

IMO if you plan to keep the car a while, pull the head and do a complete valve job. That will catch your guides and seals as well as renew the valve seats. If the engine is a 71 or earlier, you might consider hardened valve seats for running unleaded fuel.