Connecting remote office to current domain.

Currently I have a Dell poweredge 1900 running SBS 2003. For network we have a gigabit switch connected to firebox firewall (Not exact about model #) from firewall we go to comcast business class internet.

I am curious as to what you guys &/or gals feel would be the best method to get a remote office connected to our current office domain & server? We have an application that stores client information that is centralized in our main office. We ultimately want to be able to access this database remotely as well as documents that are shared on our LAN.

Thanks for any information in advanced. Let me know if any more details are needed.