I got an Aviaition degree from OU. AFTER being selected for SNA and going to primary, I thought that it did help out some. Besides the basic monkey skills (what IFS should do for you), I had a solid understanding of Instrument Flying (RI's/BI's in Primary), when other people were a little be lost at first.....but by no means did I have a Huge advantage. There are some guys that get down to primary with a butt load of hours only to get bad attitudes and wash out, or do poorly. So really if you get selected, go in thinking you know nothing and can learn a lot. And be prepared to relearn a lot.
As far as selection goes.......I do not think it means crap......especially if you have marginal grades. Selection for Navy programs is anyones guess. I really dont know that much about Service Selection process, except that Grades are the most important thing period! Especially nowadays with the tight numbers, I would be hitting the books like mad to ensure a pilot/NFo spot. I think your grades only count through your first semester of your senior year, so if you have been slacking off in College to this point, you might want to consider A. working you ass off, or B. getting ready for a career other than Aviation.