Where to start?

I have been playing bass for about 6 years. I have had no formal instruction, with the exception of some help from a guitarist in a rock band I was in. Recently I have started playing with a jazz band and a gospel band. This is where the problem comes in. In my rock band, things like key changes, site reading and music theory had no meaning,we simply didn't deal with them. I have now been struck hard by my lack of music theory and ability to read music (damn that tablature). If I had known this ealier...oh well, its my own ignorance. Anyway, I was wondering if anyone had any suggestions on what to start with/ good resources to learn from (books, web sites, etc). I am going to try to get lessons from the guy in charge of the jazz band, who is an excellent bass player and musician, except he likes his trombone. At this point a technical improvement is really not necessary, I can learn the songs, it is just that it takes so long, that it really becomes just stupid.

Anyway,
Thanks
Geoff