A good mechanic?

I'm in the market for a honest (decent) mechanic. I took my car in for a routine oil change at a convenient auto-care center (convenient to my work). Since it was the first time they saw the car, they wanted to do a free analysis to make sure all is well. Since it was free, and since I knew that everything would be well as it was a relatively new car (bought it less than 1 year ago), I said sure.

Well, when they called me to let me know that the car was ready, they reported that the air filter was in dire straights and needed to be replaced. I told them to hold on that work, since it was under warranty. I took it to the dealership (who traditionally charges more $$$$$), and told them specifically to look at the air filter as I had reports that it was dirty and needed to be replaced. They said that all was well with the vehicle and that the air filter looked fine and didn't need to be replaced.

So, whom to believe? The dealer or the mechanic that's convenient to my work? For all intents and purposes, I'm going to the dealer from now on for my new car, and the convenient mechanic will lose out on my business.

Also, there is a very good mechanic shop on the corner of 4500 South and State Street (Midas) there in Murray/Salt Lake City. They have always treated me right and have never gave me a line of BS when it comes to my car care.