The plugs are completely different, and the double DIN works directly on the CAN bus, the single still uses the K-line. I do not even think the doubles HAVE a K-line any more. You'd probably need the dash harness from whatever the newer car was, or at least parts of it, to make it work like factory.
I looked into this for my '99.5, as it has a crappy aftermarket unit with the typical impossible to see tiny buttons and light show display, and wanted to just put a double DIN from one of the newer cars I have recently parted out, but it looked to be impossible on the '99 due to no CAN bus at all. At least the 2000+ has a CAN bus and Gateway, so you could *probably* make it work with enough other parts changing, and perhaps asking the Gateway to politely accept the new module on the network.