J-man I've been a distance runner for 20 years and given that you ran a 2:30 800m last winter I think you can do it! The basic principles of middle distance were laid out 40+ years ago by Arthur Lydiard and pretty much EVERY one uses it today.
Primary Rule: START IN MODERATION. YOU CAN'T TRAIN IF YOU'RE HURT.
You should definitely consult a running coach in your area or join a running club. As if anyone didn't know this but women in running clubs are generally lean and fit.
I can't give you a specific training schedule as I'm not a 1500m running coach but this is the basic idea:
Phase 1. Aerobic 12-16 weeks
You run long slow distance everyday with one run a week (or whatever your training cycle is) at least double any other long run. This build aerobic pathways. Throw in some short, moderately paced sprints.
Phase 2 Classical Hill Training 4-6 weeks
Strengthens the quads and calves.
I avoid downhills as they are very hard on the knees. You maintain the distance/light sprint work and add hills.
(usually you combine phase 1 and 2 these days)
Phase 3 Interval/Maintenance Training - Can stay in this phase indefinitely if you choose but say 8-12 weeks
You cut out the hill training, cut back a bit on the distance work and add quality sprint work
Phase 4 Racing Time! can last 4 weeks
Cut back the distance, speed up the interval work and race your sub 5 min mile.
Once you find your time slowing, it's back to phase 1.
That, in a nutshell, is the Lydiard way that produced Jim Ryun, Peter Snell, Jumbo Elliot, John Walker, Rod Dixon, etc.
Good luck!