Actually, the above is slightly dated... the NYU site has the stats for 2011.
http://admissions.nyu.edu/fast_facts/
Avg. financial aid: $20,095 (a little lower)
Acceptance rate: 29.2%
Here's a page for Stern:
http://www.businessweek.com/bschools...les/stern1.htm
In general, the acceptance rate for Stern and Tisch are both lower than the all-NYU acceptance rate.
Most people don't declare a major until later on (although obviously some people have it all planned out), and you can change your major as many times as you want, provided you can finish school on time (I'm pretty sure that's the case).
Merit scholarships are rare in Stern and Tisch... I think Stern actually ended giving out pure merit scholarships and have restricted it to merit provided you have demonstrated financial need.