I recently made the transition in the opposite direction (MTB to road). For a roadie trying dirt for the first couple times, I would suggest finding a good, short technical loop that you can ride multiple times in one outting. In addition, riding on your own I think would be very helpful. You're not worried about keeping up with a group or showing your legs and lungs and can focus more in riding through various trail puzzles. I really like finding new ways through a tech section of a trail, whether new or old. Don't be afraid to bail on something, walk back through the section and try again. Even if you don't clean it in that ride, you still have seen it more than once for the next time you ride that particular trail.

Hope you have a speedy recovery and welcome to the dark side.