Original poster wanted to know if he could improve his 5K time by more than 2 minutes.  I wanted to bookmark it here so I could find it later.

RunningAHEAD – Topic: How realistic is this goal? For real..

The initial points:

• Ramp up mileage to about 35 miles per week.
• Run mid-week 6 x 800m intervals at current 5k pace with 400m recovery jogs.
• Run a long run of at least 12 miles with a fast finish (last 2-4 miles).

His result after training was going from a time of 22:55 to 20:30 with about a month of training.