I use Hal Higdon's plan as well. I think, based on what you indicated, that you definitely need to work more miles into your long run. Going from 8 miles to 13.1 is quite a jump. That jump may be the main factor of all your soreness. A foam roller may help. Just roll out the sore spots. It may hurt when rolling, but it will help.
I got injured a couple of weeks before my first half and wasn't able to run for 2 weeks straight. I finished the race and looked like I just finished the Goofy challenge. My future half marathons during the year were much better as far as how I felt afterwards. I think a little soreness and tightness of the muscles is natural when you go all out for a race, but you should be able to walk. Make sure that you get enough protein and carbs after your race/long runs too. I met with a sports nutritionist and she suggested that I eat a mixture of 20g protein/80g carbs within 15 minutes of my runs. She also has me spreading protein out during the day -minimums of 20g for breakfast and 30g for lunch and dinner. The spreading out of the protein throughout the day helps with recovery since your body is always getting protein throughout the day. I would try something similar throughout your training so that you can practice before the race...training is not only running, but the nutrition as well.