I developed PF while training for a half marathon. I thought it was a bruise at first. I went to a foot doctor and he gave me some stretches to do. My foot still hurt so I went back and he gave me a cortisone shot. That was almost more painful than the PF. I do the stretches, which is to stand with your hands against a wall, put one foot next to the wall and the other foot farther back so you get the stretch. Hold for a count of 10. Switch feet. I usually do 10 to 12 sets of these. I also do the frozen water bottle and wear an orthotic at night to keep my foot flexed. I think the combination of these things helped. I still get some pain occasionally but nothing like it was at the beginning.
I only wear New Balance shoes. I went to Road Runner and now have a custom insert for my running shoes. I also have a very high arch so the insert really helps.
Good luck with your 5K. I'm training for the Tinkerbell Half Marathon which is in January.