I'd focus on getting the pounds off first. I was up to 182 in early '09 and lost 20 with fairly low mileage but a lot of painful circuit training (pushups, situps, pullups, burpees, large number of repetitions of hang cleans etc...)
Once I got the weight down, the running was a lot easier, but I probably pushed myself a little too hard on the speed work without the appropriate base and spent a lot of my first year getting back in shape injured.
It wasn't really until my second full year (2010) that I was able to handle the mileage and intensity of training I needed and got sub-3:10.