I replaced my swithch last year. My '69 is a RS, so the headlight switch, like yours, also has the vacuum hose connections on it for routing vacuum to open/close the headlight doors. Replacement switches are available in the aftermarket. I purchased mine from Year One and it works fine.
Only difference was that the original swithch, which I still have, had a couple of extra connections on it. The replacement switch doesn't have the extra connectors - so your first impression is that the replacement switch is incorrect. However, when you look at the wiring harness connector that plugs into the switch, there isn't any wiring at the locations where the extra connectors are on the original swithch.
My original switch hadn't gone bad, but I had to remove it when I was redoing all of the vacuum lines during my front end restoration. Once I had it out, I figured I'd go with a replacement instead of putting the old one back in (beside the basic switch operation, you have the rheostat for dimming the instrument cluster, and the vacuum connections - and I figured this was a good time to go back with new).
Glad your shaft released easily from the switch. Although I found the button on the bottom of the swithch easily enough, once depressed, the shaft didn't want to release. Had to wrestle it for quite awhile.
I don't know of any wiring diagram for the switch itself. Only thing I can find is the basic wiring dirgram for the dash which shows the wires connected to the switch, but nothing relating to the internals of the switch.
Just to cover a couple of other possibilites - are you sure it is a switch problem?
Wiring harness properly connected (on both sides) of the fuse block/bulkhead connector?
Is your headlight wiring harness properly grounded at both ends? Should be a ground connection for the headlight wiring harness, to the radiator support, on both the driver and passenger side.
Even if properly grounded at both locations, do you physically have a good ground at the connector to each headlamp? Do you have 12v to the headlamps when they are supposed to be on? Do you have 12v to the parking lights in both switch "on" positions (park and full on)? Good ground at the parking lights?
If all else checks ok, replacement switch is an option.
Good luck - Richard