never done my own, garage did it before replacing MAF but & i'll stand to be corrected if wrong...from memory garage told me....
located horizontally top back of engine, disconnect the two metal flexi pipes either side, undo 4 ? bolts & remove.
...i think
( disclaimer ) this is intended as a guide only...yadda yadda yadda
currently '06 C5 2.0 HDi auto estate Tip run and France trekker - well should be!! occupied currently by '10 Superb DSG 170 elegance- whistles and bells that work