Help in Vectra B 2.0 dt 100 hp

Can anyone help me out? I'm currently working outside of Spain with my Opel Vectra B 2.0 DTI 100 hp. Suddenly, the malfunction indicator light came on, the tachometer stopped working, and it lost a lot of power. It felt like a naturally aspirated diesel with only 20 hp.
After it cooled down, I started it up, and it ran perfectly, but once it reaches normal operating temperature, the problem returns. I've been researching on various forums, and it seems most likely to be the crankshaft position sensor.
Could someone please tell me where this sensor is located and give me the steps to replace it? I would be very grateful, as I'm in France, and garages are expensive. The problem is also explaining it to the mechanic since I'm not very good with the language.