How do you get dash assembly out?

^ what rocky said is spot on. While replacing those wiper pivot seals, lube the joints inside and all of the points on the wiper mechanism... I always thought that old mopars had noisy wipers. Nope. They are just needing lube.

you WILL make a mess. Especially with all of the old dust and worn out insulation which is a real pain.

the heater box you can rebuild pretty inexpensively too. http://www.detroitmuscletechnologies.com/heater-box-gaskets/

I thought DMT also made a wiper pivot point mod kit to add grease fittings to them but i dont see it on their website. maybe it was another vendor.

Good luck. love those dart dashes.