I'm sure Janek will have better things to say on this than I . . . but here goes.
Maybe starting off playing with jazz tunes might be a litttle too daunting.
Start with Elton John, Avril Lavigne, pop stuff where the chords usually revolve around one key centre (with the occaisional modulation) I jam along with Belle & Sebastian, Camera Obscura, because these songs, as beautiful as they are, are harmonically simple.
If you say you are already jamming with Motown then you might already be past this point. I'm lucky. I give 60 lessons a week to students who want to learn the newest songs on the radio (Fall Out Boy? Angels & Airwaves? who?) The students usually show up unannounced with CD's in hand and expect me to be some sort of "transcription service". Do this up to 30 hours a week and see where it gets you
I love me job,
Glenn
(P.S. I do work in the useful stuff too, technique, theory, etc . . . )