Check with Apple before you go further.
When Apple first came out with Remote Desktop, I tried to get it working between my home and our corporate network, which is behind a firewall and uses network address translation (NAT).
Only after a great many hours of Apple tech support did they admit that Remote Desktop had problems with our type of setup, and that others had reported similar problems.
Apple also told me that if you get a connection working across the Internet , you can still access only one Mac behind a firewall (after setting up a dedicated connection in the router). Getting these simple facts cost us way too much -- a marketing failure on Apple's part.
I hope that's all been fixed by now. Meanwhile our nonprofit organization has totally lost interest in using Remote Desktop.
Now I've got Netopia's Timbuktu working great. It's a long-standing Mac product, with features and pricing comparable to Remote Desktop. Timbuktu does what Netopia says it does, it works for our needs (including the occasional glitch), and the telephone support has been great.