Here is how I would structure 20 weeks:
First 4-6 weeks: Lots of easy distance and generally working on building overall volume. Quality days would consist of fartleks, progression runs or steady state runs when the mood struck you, but not more than twice per week, and nothing overly ambitious.
Next 4-6 weeks (4 weeks if first phase above was 6 weeks, 6 weeks if it was 4 weeks): One 20 minute tempo session per week, one track session per week and one long run per week. The speed session would be about 2 miles worth of 200s/400s and 600s at mile race pace (with the 600s being done only once).
Next 6 weeks: One tempo session per week, one track session per week and one long run per week. The track session would cycle through 800s (first session), 1000s, 1200, 1600s, 1200s, 1000s at 5k race pace with a little less rest than the duration of the intervals. The tempo session could be either 20 a minute tempo run. a progression run, or a longer but slightly slower tempo effort.
Final 4 weeks: One tempo session per week, one track session per week and one long run per week. Track sessions would consist of race modeling efforts (200 (at mile pace), 200 jog, 800 at 5k race pace, 200 jog, 200 at mile pace) and short reps (8 x 400 at mile pace). Tempo session would be shorter cruise intervals (1200s or 1600 at tempo pace) or progression runs.
For the record, this is a variation of a Daniels approach, but it shouldn't be overly stressful.