How difficult would it be to attend college full time as well as having a internship?
College is already difficult on it's own, but most people have several other responsibilities to balance while in school. Your ability to handle an internship while enrolled full time will depend on your time management skills. If you can schedule your time responsibly between school and work, you should have no trouble keeping up with school while interning.
It's important not to over schedule yourself, but you could easily make time for all your responsibilities. Use a weekly calendar or agenda and schedule school time, study and homework time, work time, personal time, family time, and anything else you want to have time for. Make sure you know how much time you'll need to be successful in your classes, and don't allow yourself to get overworked at your internship. Ask to be scheduled for a specific amount of time, and be realistic about the time you'll spend with your other responsibilities.
If you're taking a particularly difficult course load in a certain semester, maybe cut back on hours spent at the internship or with friends. It can be a stressful juggling act, but if you are honest with yourself about your habits, and can stick to plans when you make them, you should have no trouble handling both school and an internship at the same time.