No, a 3.39 average is not bad. It's a solid B, which is always considered good work. I graduated from high school with a 3.33 and still ended up ranked #30 in a class of 444.

Generally, admissions committees are more interested in the quality of classes you take. So a C in physics will look better than a B in cooking class. (No shade on cooking class, which I think everyone should take.)

I also would not worry about how prestigious you school is. You can get an excellent education, with more attention from instructors, at a lesser-known college. It's more important to find the college that is right for you, not someone else

Good luck.