The evaporator core is under the roof above the operators station along with the heater core and blower motor.
The roof will need to be removed to access these components.
I don't recall it being that hard,but have yet to remove mine.
The cab air filter is accessed from outside the cab.
Standing behind the tractor look above the rear window in the middle of the roof panel.
That is the filter that can be removed with a few fasteners.
That filter filters the outside air when the recirculate/outside lever is switched to outside.
That lever is above your head at the rear of the cab.
All this is covered in the cab supplement for the operators manual.
Good Luck! It's hot out there!