Natively, the iPad only prints to wireless printers that support AirPrint. HP is the major supporter of AirPrint at the moment and others will presumably follow. I think that there is at least one Epson printer so far but it is unlikely to be the one that you have. AirPrint is only available on iOS 4.2 by the way.
I think that Epson has a print app (from the AppStore) that supports a limited range of Epson printers, direct from the iPad. You might have better luck there.
Failing that, there are 3rd party print apps that I think almost always work via a Mac or PC.