Change default contacts/calendar app?

[yourhums]

Forgive me if this is a newbie question.

I'm planning to root my Mototola Droid 2 (VZW). I use Deja Office but I have problems keeping contacts in sync with the native Android contacts app. I've noticed contacts disappearing from the Android contacts when other contacts are updated in Deja Office. Is there a some way to make Android use the Deja Office app and bypass the native Contacts and Calendar apps altogether after I root? I am hoping to have Android query the Deja Office database for caller ID info. If I keep sync with google contacts that would be gravy. I think the Deja Office apps are much better designed.

Thanks!