I would be surprised if installing 3D Lights Redux did cause a problem with Weapon for FSX. Doing a reinstall/repair of Weapon should fix it up (except the sound problem) and should not cause problems with 3D Lights Redux.

The is a fix for the sound problem with weapon, you get it by submitting a ticket to Captain Sim Support system:
Check-in to Your Profile > Select product > Customer Support > Search KB or Submit New Ticket

Mark