Yes, that would be a good idea given the age of the truck.
no , the heater core is for your heat , the evaporator core is for your air conditioning ( cooling )
The dash has to be remove and the evaporator/ heater case has to be removed and separated. This job is best left to a repair shop.
It should be located on the evaporator case.
Yes, both the heater core and evaporator are in the HVAC housing, which has to be removed to access either.
Before CHanging the Heater Core, have you tried flushing it? I have a 99' Jimmy and have to do this every year to get my heater to work.
Heater core is on the passenger side behind the glove box, this is also the location of the air conditioner evaporator core.. they should be in the same housing.
The evaporator is in the A/C heater box under the dash.
The entire, and I mean ENTIRE front dash has to come out to remove the heater box which then must be disassembled in order to replace the evaporator or heater core. Not a job for the feint of heart.
The heater core and AC system aren't connected.. the only component of the AC system located near the heater core is the evaporator.. so long as you don't try, say, prying out the heater core carelessly, there's nothing it should do to the AC system.
No, you do not have to but you should inspect the hoses and replace any that are questionable. Cracks, bulges, soft spots, are all signs they need replacing.
Changing ac components under the hood should not cause a chemical smell. If the smell changes by changing the air settings from recirculate to fresh, then there may be some chemicals on the outside of the parts. It is also possible that you damaged a part of the heater core system and the smell is antifreeze.
The ac evaporator is located inside the heater housing under the dash on the passenger side.