Where is the blend door actuator located?

Okay, that would be the mode door actuator. It's actually not hard to replace on that truck. Setting in the driver's seat it is up in the dash above the gas pedal. To access it you need to remove the sound deadener panel above the footwell. Then you can look up and find the actuator mounted to the end of the HVAC case. Remove the electrical connector and the screws and remove it. Now to install the replacement reverse the process except it will come in Bi-Level mode. You need to adjust the doors to match that before you install the new part.
Now you need to calibrate the system. To do that without a scan tool you remove the HVAC fuse B for 20 seconds. Now plug it back in and start the engine. After about a minute you are done.

Depends on the actuator. The mode door is about the only one you can access easily. The rest require the removal of the instrument panel to access them.