For terrain, I think you need the "W" upgrade. there's quite a bit of
discussion of this below, but the basic info is about 3 AMUs, change
software, change GPS antenna, change antenna cable, new 16mb data
card, new Jepp Jsum software for USB downloads, terrain download from
Garmin, new USB device from Garmin.

I believe that the CDI on the nav page is GPS only. You can use the
GPS/CDI switch to control the mechanical CDI.