Beginner C-C

I need to join some sort of team this year in high school, but I have to avoid contact sports from a shoulder injury and I don't want to cheap out on myself with something like table tennis or curling :S 

Cross country seems like a good bet, but I'm intimidated beyond belief by the beastly runners that are already on the team :|.  Apparently sr girls run 5km during meets, and I hear an acceptable time is like 24 mins. That's a problem because I swear I can't do it in 30...

I've been running at a light pace pretty much every day this summer for about half an hour, along with an hour or two of biking like once or twice a week (not intentionally for training tho, but my legs are always dead at the end), but I'm still not at a C-C runner's level. 

Is it possible to try and shave a minute or two off my 5km time in a couple of weeks with the right training routine? If so, could someone please direct me to said routine :). These girls scare the crap outta me, I don't want to be coming in last place! Bah.

Check out the SmartCoach over at Runner's World.  That will create a customized training plan for you based on information you provide.

it also helps to run with other people faster than you... and drink lots of water during the day.