Real quick pics of a thermostat change in a MKII T. There are only 2 bolts holding the thermostat in place, but there are some peripheral items that removal of will make the thermostat job much easier.
#1: Remove the oil filter
#2: Remove the Oil Dipstick Tube Retainer Bolt 12mm
#3: Remove the 2 10mm Thermostat Housing bolts with a 10mm End Wrench
#4: Remove the old thermostat and replace with new one and new o-ring that slips around it’s edges. Place the jiggle valve facing the notch in the Thermostat Housing, and reinstall everything you undid in the reverse order.
#5: Fill the overflow tank with water, and fill the Pressure Cap hole with 50/50 Water and Coolant. Start car up, check for leaks, start car again and let it idle for 3 minutes, check for leaks and air escaping coolant system. If none, let the car warm up, check again, then take a short drive. Watch temps carefully for a few days.. All done.