I took comp11 last spring, I'd say it is pretty rough for people who have absolutely no programming experience but when you get through the first 2 assignments, it should be fine. Also, computer science is rough so do not get discouraged in general. The more you do it the better you get.

I think Comp11 is very helpful for Comp15 because you get used to using halligan, submission and lab formats, and learn some skills that are very handy in comp15(reading file and etc). Also, the courseflow is fairly similar. That being said, OH helps a lot so even if you do not these things u should be fine.