I ordered my GPS base from www.lrseries.com The part number is XUC000030. First unscrew your am/fm antenna from the GPS base. You get to the GPS base through dome light. Just take the cover off and then remove a few screws. It is quite easy to replace.

I have a 2002 HSE and just had the same problem. Check your lat & long screen to see if its working. Mine was locked up on a certain lat & long and then I disconnected the battery and then it read all zeros or something like that. Anyway, I solved the problem by buying and installing a new GPS...