PPTP through cable modem or T1

I have an NT 4.0 Server SP5 running RAS and can access it through a dialup modem using PPTP with no problems other than being painfully slow. I would like to do the same thing using either a digital cable modem from home or using a T1 connection from a remote office. I’m not sure how to set up the RAS client to use the local LAN to access the Internet and then connect to the remote host using PPTP. Any help would be appreciated.