Tabs are good for melody, but, for harmony (chord work) I move from tabs to playing the chord shown on the sheet music. Check out the book I list below.
The book Guitar for dummies is a good place to start.
http://www.google.com/products/catal...d=0CG8Q8wIwAA# Yep, page one and don't skip pages. You gotta learn how to tune this beast.
If you play by rote - what is written - you can get by with no theory at all, just play what is put in front of you. However, if you want to be able to understand music and know how it thinks, yes, then you need some theory.
Here is one of the better papers on music theory.
http://www.billygreen.pwp.blueyonder...20Advanced.pdf The first 20 pages covers the basics, the next 60 pages get into intermediate and advanced theory. Enough here to keep you busy for the next year or so.
Have fun.