ATLskierDealers are always more expensive than other shops and they almost always do more service than needed.
Just take your car to pep boys to have the codes read, search subaru forums and YouTube to see if you can do it yourself, and if you can't you can bring it somewhere else.
I've been doing this for a while now! I have the P1443 code which is incredibly difficult to troubleshoot, and I had some cylinders misfiring so I changed my spark plugs but it still isn't idling well.
Thanks for the heads up about The Mechanic Man though!