Thermostat is located above the alternator and below the power steering pump.

You will need to drain the cooling system - theres a plug in the bottom of the rad.

Remove the power steering pump.

You should see a hose connected to a housing attached to the block.

Cover the alternator to stop it getting too wet, and remove the hose from the housing.

Remove the housing, 3 bolts if I remember.

Replace the thermostat.

The old thermostat should have a "jiggle pin" in the top.

The last 3 thermostats I have bought haven't, which the first time caused an air lock in the system.

I drilled a small 4mm hole and put a very small bolt/washers/nut on, which allowed the air to escape without letting the coolant through.

I would also suggest replacing the hose clips with jubilee clips etc, and use some gasket sealant on the housing.