I have to take off the thermostat on my vw 2000 golf.

The thermostat on most vehicles in located on the motor usually where the upper radaitor hose goes in to the motor (you may have to remove the plastic cover for access). You will see a round housing not too much bigger then the hose. 99% of them are just 2 bolts and it comes out. Make sure you observe the way your thermostat is sitting (only goes one way) to put it back the same and replace the gasket with a new one to avoid leaks. Also don't overtighten, you can easily strip the bolts then your really gonna have an issue.

Can say the 2003 APK 2.0L engines thermostat is located almost vertically behind the alternator, for the job you'll need sockets 10mm and the elbow joint extension for the lower bolt on the thermostat housing. the jobs a little fiddly but made easy with the elbow joint.
care is to be taken when retentioning the plastic thermo housing as it easly breaks and a replacement isnt cheap So just use common sense when re-tightening
others report using the TDI thermostat as its cheaper