How to change a lambda sensor?

Please please help, can anyone tell me how to change a lambda sensor on my car, as I have been waiting for about 2 months for my boyfriend (who now isn't talking to me) to do it and my car is really running terrible, I have a 1.4 (52 plate) VW Polo, the sensor is the one behide the catalytic converter, is that at the front of the car of back? please help as I can't afford to take it to a garage (I have already brought the part, just need to know hoe to fit it)How to change a lambda sensor?Get a new boyfriend preferably a mechenic.How to change a lambda sensor?your lambda sensor is on the exhaust before the cat converter , it simply undoes with a spanner,after you remove the wire connectionHow to change a lambda sensor?The lamda sensor, also called an oxygen or O2 sensor, is located in the exhaust pipe before the convertor. This is located near the front of the car. These sensors are usually rusted in very tight by the time they wear out. This may not be something that you'll be able to do on your own as usually a torch is required to remove the old one.

Also it is very rare that a lamda sensor will cause extreme poor running conditions, usually the issue is with high fuel consumption. The lamda sensor could cause the spark plugs to become fouled to the point of causing poor running though.