Remove and replace left and right valve cover gasket (both sides), remove and replace spark plugs, replace front camshaft plug, remove and replace oxygen sensor (one)

I had my car checked here. They did the following: Remove and replace left and right valve cover gasket (both sides), remove and replace spark plugs, replace front camshaft plug, remove and replace oxygen sensor (one). I paid for about 2,100 dollars including the full checkup and I had it on their financing. As a person who has no knowledge of car parts, I trusted them fully. I just hope that what they charged me is a reasonable price. Will start bringing my car to their shop for some maintenance i.e oil change etc. Hopefully, they will take good care of my car as what they promised me. Thanks!