You are faster than I am, but I have been running for a long time/ You can do an 18 minute 5k right now. You can do 4 miles at 6:09 in a no race situation. Throw in race adrenalin, a shorter distance, and good strategy and will make it. Runners world did a piece a few years back about 5k pacing. They found that runners who go out a little too fast and then do their best to hang on get the best times. Try a 5:30 pace for the first mile and try your best to maintain it. You will probably fade a bit, but it will work out. Do your intervals at 5:30 or faster. Have fun!