Well obviously you're at the point of replacement now; so 5lb sledge hammer it (them) off! Rotate as you bang away!! Be certain to wire wheel off all of the corrosion on the hub surface & apply anti-seize before installing the new set. Check your calipher piston seals for leaks. Also, observe if the wear pattern is even on the pads. If not, the master cylinder may not be delivering even pressure through the system! Change out completely the old fluid & use DOT4! See the link provided:

http://mb.auto.pl/index.php/Dok.-serwisowa-CD2.html