run forest, run.
congrats! it's a blast. i've not run the 'land race, but have run the 'world before, a great race with much fun to be had.
a big part of distance is mental, that's to say, you must decide to do it and then believe you can through training. another big part is where you are starting from. fit and running 5ks already is different than overweight and unable to walk around the block. i recently went through this with my brother-in-law. 8 weeks to get him from couch to first 5k, then he got really excited and into it. i took him through a 6 month 1/2 training plan that went from 15 miles p/week at the beginning up to 35 miles p/week before a 2 week taper prior to the race. he was able to finish his first ever 1/2 at just over 2 hours, and now is hell bent to run another under 2 hours. he also started eating better, taking lunch with him to work and has lost about 25 pounds over the last year which has helped with him working toward a faster pace. it's been fun to help/watch/encourage.
the link above is a great site, active.com is another to check out. a lot of the training plans are about the same, find one that fits your schedule and level and stick to it. it's all about 'time on toes' and 'building base miles' at the end of the day. going into the race knowing you've done the training and can easily finish is way more fun than showing up nervous!
get good shoes. from a real running store, and with the assistance of someone who can do an actual gait/stride analysis. there is a huge difference between support/neutral/guidance/control and fit varies a lot between brands. the wrong shoe can really do you lots of damage, make running no fun, or worse. there is no best shoe, only best shoe for you. (Brooks are the best...)
happy to help/answer if i can. i run lots... several races so far this year, and will be running a couple longer ones later this year.