theres some good video clips on bumper removal on you tube, to explains it better than words, but its comes off in minutes, you will be surprised, but you could always get someone to rev the engine and listen low down by the front grille, see if you can hear air escaping, plus if you can see any oil smears on the radiators, that's a good tell tale sign too of an intercooler leak.
yes its sandwiched between the water and air con, but easy enough to separate without removing all 3, so you can just ease out the intercooler and swap it. have plenty of gloves to hand if it has gone, it take a long long time to wash diesel oil off your hands afterwards, LOL.
