There are a bunch of various threads on all sorts of forums about this and even some videos but I have seen so many variations it's surprising and I wanted to add in a few tips gleaned from my own experience and watching a few videos from some really dumb people. This should apply to any SuperDuty or Excursion from 99-06. I have seen threads from some people saying the same heater box is carried over onto later years but I cannot confirm that. Also, this is for the blend door actuator motor only. If you have a problem with the door itself that's going to need more searching on your part....and if you have an Excursion this is for the front only.
First, you do not have to remove the dash. Let me repeat....you DO NOT need to removed the dash! I have seen threads and videos where people say you have to because there isn't a lot of room. They're right, it's tight in there, but you can still get it done. All you need to do is drop the glove box by emptying it and then pushing in on the sides, allowing it to rotate even further. BTW, the motor in the picture is "white" but yours may be black. From my reading I think it's the difference between manual and automatic temp panels.
Second, you do not have to remove panel in front of the heater core....that's the one on the right side of the pic above. There are about 8 screws holding it in place. You can change the motor without pulling that. However, pulling it does make it easy to check your blend door. Once it's off you can reach back there and try moving the door while the motor is still attached. If the shaft is cracked it should be fairly obvious.
Third, you don't have to remove the entire assembly, just the motor. This seems like a no-brainer, but let me explain. Here is the part that is bad....actually, the bad part is a gear inside this, but you can't just buy the 10 cent gear. You have to buy the $50 motor instead. Grrrrrr
But as you can see in the top pic it is sort of inside another component. In fact, when you purchase a new motor it will come installed onto that new bracket....like this:
You may think you have to remove the whole thing since that's how it comes, but you don't have to. There are three "pop pins" holding the motor in place. You can see two in the pic above circled in red. The two in front are easy to get to. The one in back (on the right in the pic above) is very difficult to reach if you have large hands....impossible if you have XXL hands and are trying to hold a tool. It's no worry. Just pop the front two and then wiggle the motor while lifting up/tilting back. That rear pin lets go easily. After that just lift straight up. Oh...to pop the pins use the a 5/16 or 8mm socket. Just push the socket down and then lift/pry up on the motor.
If you want to remove the whole assembly, or if there is a need because yours is cracked or something, there are two screws to remove. One is right in front and obvious. The second is shown by the green arrow in the pic above. It's a bit difficult to get to but can be done with a small 1/4" ratchet. Once you get those two out there are two more which must be loosened a hair. They go in these slots as shown on the bottom, and, of course, to get to them you have to remove the motor first so that just seems silly...again unless the part needs replacement.
I think the original idea was to be able to rotate that and leave those two screws installed but loose. Let me just put that idea to bed right now. It is NOT easy! Don't do it unless you have to! Engineers put it there because they love to torment mechanics!! lol If you do have to replace the lower piece don't loosen those last two bolts. Remove them completely. And when you're putting it back in place the tray in there first, line it up, and then put all four screws back in place. Don't bother trying to do Ford's sinister hand yoga with that thing.
Replacing the motor itself should be pretty easy right? Just drop it in place. Well, not quite, or at least not if you're me. It will go into place, and it will click onto those posts, but it might not work. As silly as it seems it appears the motor is really weak and the slightest binding of the gears can make it not rotate. I tried a whole bunch of things after my initial install and it just would not turn. I pulled it out and did a quick function test. Worked 100%. When I went to put it back in I could tell it was lined up, but it felt like maybe it's wasn't the best it could be, so I put the climate control at all the way cold, placed the motor's shaft into the hole until I could feel it resting on the blend door and then I turned climate to full hot. The motor's shaft turned and just before it reached full rotation to the hot side the motor just fell down into the slot. Just another slight bit of pressure and the three tabs clicked into place as well. That made all the difference. Everything now worked as it should.
It seems weird, looking back at it now, to give out tips for something which should be so simple, but I have seen and read so much bad information that I'm hoping I can save someone the hassle of doing a lot of unnecessary work. I mean, I saw on where the guy took out the entire dash and one where someone cut the motor bracket.....just to replace the motor. All of that really isn't necessary if you just use some time to think and plan the process.