SBS 2003 Exchange

I am starting a small busienss, have beginner knowledge of sbs 2003. have a host company running my .com site and email but want to use exchange in sbs to get emails from there. the sbs has a .local domain. i am behind an adsl line w/ dynamic ip. would like to get emails from hosting company to exchange and then allow access to the exchange accounts for mobile phones (ie: blackberry/palms) as well as calender sharing etc…; would also like to get web access to the exchange to check emails. how do i do this? (dyndns?) any help would be greatly appreciated or any pointers to good tutorials/books to tackle this.