Hi:-) Anyone who have a instructions how to chane a ac compressor on a 2006 Commander 3.0 crd?

Hi, could anyone advise me on whether a remap would see a slight improvement on mpg? I have found a very reputable remap company in the UK (Atlas remapping in Somerset) who will also give a half price engine carbon clean included with a remap. Thankyou for any advice in advance.