About to turn 50, out of racing/training from 1984 to 2003, I feel as though, after five years of figuring out what works and doesn't work, I'm finally starting to get it almost right.
I'll second the good advice you've received above. Give yourself time to ease back into the really hard stuff. I ran myself into the ground with a tibial stress fracture one year into my comeback. Bones are slower to adapt than muscles. Avoid concrete; cultivate softer surfaces. 600-1000 mg calcium a day helps me.
8-10 on Wed/fri, 13-15 on Sunday, easy 3-4 mile jogs the other four days works for me. Find what works for you.
Easy base mileage, progression runs, in pre/off season; then some longer tempo runs (4-5 mile) at or a little below threshold; 3 x mile at 10K pace w/ 2-3 min. breaks. Closer to serious racing, I did 9.5 miles this morning with 5 x 800 @ 3-5K pace and 2-3 minute breaks. I run by heart rate on faster stuff; this morning I pushed to 93-95% of max HR on the intervals.
Lots of hills are good and quickly strengthen you. Avoid hard downhills; they are tibia-killers.
One favorite 10K workout is a 4 mile tempo/fartlek run with 3 minutes hard / 3 minutes float. Hard is at 10K pace; float is relaxing until HR comes back down to just sub-threshold.
Another good workout: 3 mile tempo/fartlek, alternating 400 hard (5K pace) with 400 float.
But sometimes I'll just do regular 3 mile tempo runs and keep it right at threshold.
All of these workouts have helped greatly. Research online; there's a great series of training papers on a UK website; google "10K training." One paper compares tempo runs with intervals workouts; intervals are clearly superior in terms of helping you achieve your best race.
I never run on the track. I make use of what I've got.
Good luck!
Oh: on the long run, sometimes it's great just to run LSD pace the whole way; often I'll pick it up to sub-threshold for most of the second half. Closer to goal race, I'll sometimes hammer the last few miles. Figure out when each of these sorts of long runs works best. That takes....oh, about five years.