how do I change my heater resistor pack on my 2003 vauxhall omega saloon?

If your fan is only working on the fourth speed then it's the heater blower resistor. Usually located behind glove box on most cars. Normally looks like a plastic disc, with a resistor on it. The last one I changed was on a Laguna, think I turned it & then came straight off.
If you had a test meter you could test supply to heater blower motor, then to resistor

George.
November 2008