>I will soon be getting DSL service at home to replace my dial-in to an ISP. Am I at any risk and should I be looking at getting a firewall???

You are at a great deal of risk. Script kiddies can ping (scan, to put it more accurately) your box, and if you've got a static IP address, they can come back later after they've established which IPs are open to snooping.

In the case of what originally started this firewall discussion, hackers allegedly nabbed Whistler source code because some Microsoft employee left their home connection to MSFT open all of the time. If you don't connect to your corporate network, and don't care about what happens to your home box, then don't worry about it. Otherwise, check out Zone Alarm (or Microsoft Proxy Server, if you the heavy armor).