Not quite.
With the Core Duo -> Core 2 Duo, all it took was changing the CPU installed in the socket and a firmware update for the EFI.
With a switch to AMD, they would have to switch chipsets, add a 3rd party WiFi chipset (since AMD doesn't manufacture any, and Intel is starting to integrate that functionality into their own Southbridges, like in the future "Bearlake" family), new GPU and/or IGP, slower adoption of Intel-backed standards (like PCIe/PCIe 2.0, perhaps USB 3.0, 802.11n, SSE4, DDR3 and beyond, etc).