As a preliminary step, you may wish to pull the current radio to verify sufficient depth for a double-Din setup. On 1997-2002 Expys, a bracket behind the radio has to be removed (cut off) to accomodate double-Din. Otherwise, available room diminishes from double-Din at the faceplate to about 1.5 Din as you look back into the cavity.
Again, this info is in regard to pre-2003 models, so it may be moot for you. But I would verify anyway.