I bought a new Sony tv over 4 years ago at Best Buy but declined any help from the Geek Squad to set it up. I realize it's a bit late to ask for help now that I would like to have the tv mounted on the wall, but can I hire them to do it for me?

The short answer is yes, however you may want to call them they change up the service quite frequently

I havent experienced this given situation first hand, I do know however that in years passed I had a friend purchase a new TV, pay for the set up and purchased set up for a second tv be already owned and they performed both installs/mounts even though only one had even been purchased through them.