Well Ted, I'll give it a shot based on my general knowledge of these systems. Sheathed control cables are usually attached to the heater box or support structure by a retainer strap or clip and screw of some kind. Usually to remove the bent end of the cable from the lever you will need to free up the cable from the retainer to be able to rotate it enough to get it detached from the control lever. You will probably have to remove the whole control unit to get the cable off of the switch. If you can get at it, try your idea of the penetrating oil, let it sit for an hour and gently try to move the cable. Do this one more time and if it does not produce any movement, you will have to replace the cable. Hope this helps.
1987 BMW 325
[This message has been edited by jeffsr (edited 07-02-2000).]