can't help you about the ex apps question, but to alter the buttons on the main screen, you can edit them under settings -> buttons (or something
).
there you can chose what button 1 does, button 2, ...
for the navigation question: take a look under settings -> nav. there you can disable destinator as nav program, and use another (there is a plugin for iguidance, maybe others too... check the CF website under downloads)
Greetz
Dj NRG