Performing a Combat Maneuver
When performing a combat maneuver, you must use an action appropriate to the maneuver you are attempting to perform. While many combat maneuvers can be performed as part of an attack action, full-attack action, or attack of opportunity (in place of a melee attack), others require a specific action. Unless otherwise noted, performing a combat maneuver provokes an attack of opportunity from the target of the maneuver. If you are hit by the target, you take the damage normally and apply that amount as a penalty to the attack roll to perform the maneuver. If your target is immobilized, unconscious, or otherwise incapacitated, your maneuver automatically succeeds (treat as if you rolled a natural 20 on the attack roll). If your target is stunned, you receive a +4 bonus on your attack roll to perform a combat maneuver against it.
When you attempt to perform a combat maneuver, make an attack roll and add your CMB in place of your normal attack bonus. Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver. The DC of this maneuver is your target’s Combat Maneuver Defense. Combat maneuvers are attack rolls, so you must roll for concealment and take any other penalties that would normally apply to an attack roll.
If you use a weapon to perform a combat maneuver, you can add any bonuses that you can normally add to an attack roll and it will apply to the Combat Maneuver. So yes, if you perform a Trip with a +3 weapon, then the +3 bonus would apply to the CMB roll. You would also add any bonuses from class abilities like Bard's Inspire Courage, spells like Haste or Bless, and feats like Weapon Focus.
"Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver."
I would say the enchantment bonus of the weapon used is in "other effects".
Any time ;)