Well, I survived the Heat Box removal attempt, and so did the Heat Box (miraculously), although I could not get ALL of the heat box out unless I disconnected the A/C evaporator hoses so that the evaporator could be removed from the heat box - YES, the evaporator slides into the heat box so that it is IMPOSSIBLE (without a Sawz-all) to remove the heat box in the service manual prescribed manner without removing the evaporator 1st. Something the Service CD does not tell you.
Anway, I removed the bottom of the heat box (after finally locating all the metal clips that hold it together) and once the bottom was out, I could remove the Front half of the Heat Box (the piece that covers the heat exchanger coil). Again, several metal clips, 4 of which cannot even be seen until the Heat Box bottom is removed.
Once the Heat Box front was removed, I was able to see what the problem with the "stuck flap" was and I'm working on a solution for that. The Heat Box is quite a contraption. Seemingly pretty well built, but nonetheless quite a contraption. I don't know that I could have done to design any better, but....
It would have been great if the CD would have had some pictures showing the inside of the Heat Box so you could get an idea of how the box was made. I believe that would have been helpful in taking it apart.
More to come as I make my repairs and put it back together.
Regards,