Received the thermost from you in 2 days. (fast and reasonable shipping)
Removed 2 control knobs and front cover.
Removed 2 screws holding controls mounting plate. (About 3 X 6 inches in size)
Removed 2 screws holding thermostat in place.
Installed new trhermostat.
Checked the RAC and all was OK.
As a matter of fact, I had to wait for the wife to finis...