Yes, 2d experience is a very good asset to have. Alot of studio's want more than just a 3d modeler, they want someone who can where lots of "hats" I would suggest drawing on napkins or carrying a sketchbook with you. You don't have to be great at drawing, but you should work on it.
Your not "doomed" also for the no education thing. More game studios are looking for college graduates, but if you have an amazing portfolio you could get it easily. Just remember, the bar is being raised every year on what it takes to get into the field.
The biggest thing I can say is head over to conceptart.org. Register there and just start posting your sketchs's people are soooo friendly and willing to help you with anything you need.
You gotta start somewhere.
Research what companies want in their employees and hone in on those skills.