Congratulations!! 5K events are great fun!
As far as stretching goes -- this web link has some great stretches with photos:
http://www.halhigdon.com/15Ktraining/Stretch.htm I find it's easier to see a picture than try to explain it!
I do have one suggestion for your training plan. Instead of doing the same distance every time, it is helpful to pick one day as your "long distance" walk/run and gradually increase that session up to your planned race distance. That way, your body gets used to moving that far and you have the confidence of knowing that you can do the distance without difficulty.
Good luck!
P.S I just re-read and realized that your races are coming right up!! You'll be fine, just don't overdo the training beforehand if you aren't used to going that far. Don't worry about speed, just enjoy it!