Hello, this one is not too bad to do. I am sending you instructions from the Venture service manual. You are correct, fogging of the windshield does indicate a leak in the core. Start on the inside of the truck. First is instructions to get to the core cover.
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten Tighten the screws to 1.6 N·m (14 lb in).
Tighten Tighten the nuts to 10 N·m ( 89 lb in).
J 38185 Hose Clamp Pliers
Tighten Tighten the screw to 1.6 N·m (14 lb in).