Mode door acuator replacement

I have a 2001 Safari, 2wd, 4.3 liter gas motor. I have to replace the mode door actuator that diverts AC and heat to the dash vents or the defrost vent. Right now the venting is only to the defrost and floor vents. AC works good and suddenly quit. Any pictures or steps on how to handle this replacement?

Is the actuator electrical or vacumn?

Thanks

Grant