Thermostat replacement directions 4.2L

Looking for directions on thermostat replacement for my sons 02 Trailblazer, believe its 4.2L. Does the main belt and power steering pump have to come off to get to the lower bolt? What else needs to be removed and what "tricks" are available? Also the auto parts and the Chevy dealer have been trying to supply a replacement that will not fit it looks as if it will hit the power steering pump. Did get the OEM GM-numbers off the original tonight. This may help with proper replacement.