00 Blazer heat issue
 

Hey all,
I have a 00 Blazer with no heat, it just blows cold air. A friend of mine checked the thermostat and flushed the core and said that neither was the reason for not having heat. He recommended checking the heater control/actuator but he said it was under the dash and was a pain in the ass to get to. Is there a diagram anywhere to show how to replace or at least check this part?