Hi skeeweeaka,
If you are simply seeking to change the eBay account associated with your Auctiva account, you can accomplish this by generating a new token at Auctiva -> My Account(Tab) -> Ebay Settings, by clicking the "Get New Token" link.
However, if you are looking to transfer listings from one eBay account to another, I'm not sure if you will be able to accomplish this. If this is the case, I suggest you contact eBay support.
-Mike