How do I change my thermostat for a 1999 Ford Expedition?

It is under the PS pump reservoir. Remove the resevoir, remove its mounting bracket, remove the thermostat housing bolts and housing, pull the t-stat out, clean all old gasket materials, replace the o-ring, and replace the t-stat. NOTE: Make sure the air valve on the t-stat is in the 3 oclock position. I have attached pictures of the air valve and the location of the t-stat.