If a character has the Weapon Finesse feat, and is wielding an appropriate weapon, is the Combat Maneuver bonus changed to include the Dex bonus, or not? How about for Combat Maneuver Defense - would you include the Dex bonus twice, or does it stay unchanged?
Yes, but only with disarm, sunder, and trip attempts.
Having the Weapon Finesse feat allows you to substitute your Dexterity modifier to your Strength modifier when determining the combat maneuver checks made with an applicable weapon (as stated in an answer about Weapon Finesse on the official FAQs). Remember to also apply the armor check penalty of your shield, if any.
If you like a more universal approach you could take the Agile Maneuvers feat (which substitutes your Dexterity modifier to your Strength modifier when computing your CMB with all maneuvers (from bull rush to trip).
Neither Weapon Finesse, nor Agile Maneuvers affect your CMD.