I can only answer the first part of this personally. i started community college during my senior year of high school, just doing night classes. so all of my friends were still around at the time, i just made more in college, and that progressed, the next year i got some high school friends, well like you said, more acquaintences, and i made even more new friend from other schools.
the biggest thing you gotta realize is life is always changing. you're always gonna meet new people, do new things. some you like, and some you don't like. the trick is to make the situation into one you do like. you want the college experience, then make the community college experience. you say sheltered, sounds like you want to party. go get yourself an apartment and throw some parties! honestly, you need to meet more people in your school, i bet they are already throwing parties.