All of my A/C and heat settings blow thru the defrost vents, is there a door or something in the system that is stuck, how can I free it up?
You've likely got a vacuum problem. These cars use vacuum to change modes and a cable to change temperature. Check the vacuum tree on the firewall near the brake booster (under the hood) and the hose from it to the intake
Also check the vac hose that goes inside the passanger side wheelwell to the vacuum canister which is mounted inside the inner fender. A few years back I had the same problem with my 87 3.8. Whenever I accelerated the HVAC would go from vent to defrost. I diagnosed it and found that the vac hose was disconnected from the vac canister. I loosened the inner fender well and pealed it back just enough so I could repair the hose and reconnect it to the canister. It also might be possible that the canister could be cracked.