cross country...maybe?

I need to figure all this out. i have a friend who runs cross country, and he is willing to train me. i used to run until i got into college again. i want to run, but my knees r pretty tore up. so, im hoping he can teach me what i need to know. im nervous, but excited. running with someone new is always fun, but challenging. you have to find out their patters, their speed, etc. hes so tiny too, i know he could run to the ends of the earth and back again. i explained to him that im not sure my thick body type can do it, or is made for it i should say. i used horse terminology, haha! i said i was more like a draft horse when i needed to be a thorough bred to run like you need to for cross country.
i wonder how much weight i will loose over summer. im concerned also that there will be no change, like last time. i stayed the same. but maybe this kind of running will be different.