Looks like there is a tool made specifically to pull the wiper arms off. I'm doing the same on an Eclipse in order to repaint them black and am presently stuck with the wiper arm jammed on the splined driveshaft. Looks like the tool to do this costs about $4. Search online for a Lisle 65750 Windshield Wiper Arm Remover and you will see.
George K
October 2008