Lox [[ ... I would recommend you do it on your own and save your money.

A good exercise could be to find a note that you sing clearly and resonantly etc, and then every morning and evening you could chime it, whether on tuning fork or instrument, and sing the appropriate letter, A,B,C etc ...

5 minutes of that a day for 2 weeks and you would be able to recognize that frequency a mile off.]]
That's pretty much how I managed to tune my string-loosened guitar by ear, albeit slowly, to where it perfectly matched my tuner (when I finally found it). Basically, I kept playing and singing either "Over The Rainbow" or "The Tennessee Waltz" (or alternating them, until the sound I was producing matched what I had stored "in my head." And I knew which notes each melody started on, so when what I was producing on the guitar finally sounded "right" on that note and the other strings were tuned to the right intervals from there, the guitar's tuning matched the tuner.