Friend has a 97 850 w/ 120,000 on it. Check engine light is coming on and his mechanic says he needs a new air pump and check valve to cure car's ills, or at least make that light go away so it can get by inspection. I'm pretty handy but don't know too much about what this pump does,how easy it is to change out or whether after switching it out whether any other technical functions need to be performed following that. Can anybody give me any ideas on this ?

Also, he disappointed the mechanic by stating that he could get the parts cheper than the $850 that the mechanic quoted him just for parts. I got what he needed from FCP for far less. I usually do shop thru them and was wondering if anyone had bought the OEM Air pump they advertise for this model and whether it was of good quality?

Thanks