What’s my first step in expansion?

I started working for a small (35 node) company a year ago. We are an NT network running DHCP, Exchange, Proxy (serving our own website). We are moving from a DSL line to a segmented T1.

We have just won the bid on a LARGE project. This requires the company to open a second site about 20 miles away with approximately 20 nodes. Cost is a factor.

I need to figure the most cost effective way to connect these 2 sites. I believe that a dedicated line is too costly. But, I am not sure of anything at this point. I have been given this project and have no idea where to start. If someone could give me a hand or point me in the direction of a good text that can help.

PS – The cost of a consultant makes this service out of the question.