Getting what I want the hard way.
The new replacement had the 1.5 version of the OS on it. I spent a couple of hours trying to figure out how to get the 2.x version of the OS back, before finally stumbling across a chat link in the Apple store. After discovering the chat doesn't work in Firefox (but does in Safari) I talked to an Apple tech. He told me that in this sort of situation he normally puts the OS back in the purchase queue to let me download it, but that he couldn't do that in this case. So he is refunding me the money for the purchase, which co-incidentally happens to be the same amount as the upgrade from 1.5 to 3.0 will cost me. So I get my free upgrade to 3.0 after all. Yay!