You will need to remove any properties that are on your old login for Trademe.
Then go into a edit screen of a property- Publish Tab- Then Right click on the "Trademe Box" and select "Reset Trademe Account" now Enter in your new Trademe login Details and Save.
Then re send all the properties back up to trade-me by re selecting the tick box in the edit screen of each property. Doing the reset on one property will update Palace system with your new login details.
If you have any further questions please feel free to ask us here at Palace Support.