Exchange 2k3 & website on the same box – from the outside.

Setup- Win2k3, IIS, a website, Exchange 2k3.
Issue- this is all @ home – 1 IP address using DYNDNS as my DNS provider. How to I get OWA to run from the outside as well as have a working website with basically one IP address?
Simply Linksys router being used, but not setup in router mode. Thanks

btw the website has been running flawlessly for a year. Just added exchange and want OWA away from home.