The blend door servo motor is hidden up under the dash on top of the HVAC plenum, above the glovebox and forward of the passenger side airbag which needs to be removed for access. The factory manual says to remove the dash (!) to change it but it can be done in place if you don't mind working in cramped quarters. At least that was the case for the one that I changed in a 2003 Ranger.
, scroll down to "Mounting the Blend Door Servo".
These instructions work on several years from 95 and later. Hopefully, nothing has changed substantially from 2007 onward.