From my Pismo memories (may she rest in peace) I think you're basically correct. I remember, when I got my upgrade (I think it was a 900 MHz one) that, in order to upgrade, the CPU had to be removed from the daughter card and a new one soldered into its place. I also remember, from taking mine apart, that once you got the daughter card/RAM off, there wasn't much to the thing. There was a separate board with the audio on it and the trackpad, but most of the Pismo was CD/DVD drive, battery and HD.