You removed the caliper? You have taken out both bolts, unhooked the parking brake cable and brake hose? Maybe you meant you've removed the pads... because without the caliper in place, the rotor should literally fall off.
Do not rotate the brake arm using the bolt head. On the drivers side you can go over center and break the internal parking brake adjusting mechanism. If you have to move the arm, it should only move toward the hole in the casting.
By compressed the piston - rotated it to move it back into the caliper? It should go nearly flush the the surface of the caliper.
Without pads, the caliper should slide in and out (towards you sitting next to the car and toward the differential) until it clangs on the rotor. It may be "stuck" in position because the grease has dried. It should move at least an inch. Moving the caliper in and out should give you plenty of room to remove the rotor, which is only held on because the wheel was covering it.
The thin metal pieces are anti-squeal shims. They should reduce brake noise. They should be attached to the new pads, rather than reuse old ones.
Sorry, now need my beauty sleep for tomorrow's NY/CT-NJ AX battle. If you get stuck, call me at 845...235...6392. I'll return your call during the day.
