'87 Heater Distribution Box Access

[constructo]

I'm experiencing a heating problem with my '87-S10 w/o AC. I think I've traced it down to a broken link on the damper/valve inside the distribution box set just in front of the floor console, mounted on the firewall, 3/4 under the dashboard.

When I change the control panel settings between FLOOR, VENT & WINDSHIELD, I can hear the damper moving. Then there's a clunk, but nothing changes. I am getting a low flow of warm air to most locations, but I'm not getting anywhere near the volume I used to get.

I've needlessly replaced the heater core as a preventative messure - It was OK, but got damaged in the removal process. I had to flatten the piping in order to remove the hoses, which was too bad because the replacement core is not near as good as the original equipment. All it realy required was a good dusting.

Once I removed the shroud covering the heater core under the dashboard, I was able to see into the central distribution box. What appears to have happened is that the hinge pin which ties the actuating arm to the damper (connected I think, to the vacuum control valve located on the left (driver's) side of the distribution box) has broken off. As the arm passes by the damper's lever arm, it snags on the hinge pin and attempts to lift it, then slips off resulting in the clunk sound that I was hearing. I need to be able to get into this distribution box in order to repair or replace the hinge pin. Can I do this without removing the entire dashboard?

Thanks in advance.

Any and all help is greatly appreciated.