Should be located in a removable housing at the engine end of the upper radiator hose Drain about 1 gallon of coolant from the radiator
Remove this housing
Make note how thermostat is installed
Clean both surfaces
Replace thermostat and gasket
Re-install
RE-fill coolant slowly to prevent an air lock
Start engine and look for leaks
Run engine to normal operating temperature with heater on
Re-check coolant level
the heater motor is under the glove box, pull out lower cover and remove side kick panel and and heater will be mounted with 3-4 screws becarefull when lowering blower motor, the fan cage is plastic and may break, I had this happen to me,
Only if you replace the Dryer, install adapters on the lines, and use compatible oil.
dependes on the car
eBay
Code 12 is a period It flashes when the codes start and end so you will see code 12 usually three times, then the codes you need to fix then code 12 three time and the codes you need to fix will repeat and so on.
Under drivers side of dashboard
no idea
Mounted on top and inside the fuel tank.
Check the owners manual
yes it will fit 1991-1994 models.
sticker underneath the hood
more than likely if your state requires emissions testing.