My complete support to you. There is no rocket science in binding adjustment, and you can do it as well and probably with more care than the overworked and underpaid kid in the shop. In fact, that used to be the case, as a kid I remember that Marker bindings were sold with a paper peice showing the locations of the holes and a (completely useless) chart for binding settings. So you just knew your setting and tend to go by it and adjust it when things felt wrong.
Just to remind the outraged "get it done by a pro" crowd- the retention setting is based mainly on the diameter of tibia bone. When was the last time a shop measured that for you? I am quite comfortable adjusting my own binding and my family's bindings as well. I typically agree with what the shop sets, but if I feel that something is wrong, then I won't hesitate to take out a screwdriver and turn those screws. If your skis are flying off in mid-turn or if the binding didn't open when you feel that it should have, it is time to correct things.
P.S. The one time my wife tore her ACL, she was on a rental ski adjusted by a "pro". (I do know that ACLs are not binding-related)