Hi Jay -
A couple of quick answers:
1. Yes, many/most groups choose their large fall fundraiser in the spring. Depending on what part of the country you're in (south works a bit earlier than northeast, for example, since southern schools are often out earlier), March is a pretty common time. There are some nice early-sign-on bonuses available in the spring.
2. Yes, most of the fundraising companies have reps. who will come out and work with you. Use that, interview reps., get references.
3. How do you find them? Well, I'd wager your post here will get you a few emails.... :0). You can also use our Fundraising Yellow Pages on this site:
(Click Here for Yellow Pages)
These guys want your business. Look for quality and reputation and service. Don't base your entire decision on profit percentage.
Ask more questions here; you're sure to get good insight.
Tim