Being high milage I wanted to change the thermostat as I had no History. only $15. The thermostat shown is for the aluminium housing only. # AJ86484
Do not drain the radiator just remove the three bolts holding the thermostat housing (* 8mm) and pull the cover forward and up with the main radiator hose still attached. Minimal loss of water as the thermostat blocks the hole in the cylinder block. If the old stat has failed ..they fail open then you may get more water loss.
Clean and prepare gasket using a sealant.

You can see the old thermostat in the centre about 2/3 down held by its rubber gasket
Pull out the old stat and immediately push in the new one . do not remove the header tank cap to minimise water loss. Fit the stat cover and bolt up the three bolts . Top up and run engine to clear air.
NOTE the original stat was 87deg C and all the new ones 84 deg C