You are correct. The mount needs to come off. (Guys..i't'* pulley #9, the SC idler pulley)
The procedure is to jack the passenger side and remove the front wheel. Under the body side of that mount are two 15mm bolts. Loosen them, do not remove. Put the wheel back on and lower the car. Use a piece of wood under the oil pan to distribute the weight, and use a jack to lift up slightly. Remove the main bolt from the center of the body and engine side mounts. Lower the motor slightly to relieve pressure on the body side. Remove the two remaining bolts on the body side (look straight down at it from above). Lift up and wiggle the body side out. This gives you room to work on the engine side. Remove the bolts holding the ps pump to the engine block (2 13mm'* one at 12 o clock and the other at 6 o'clock) by going through the holes in the pulley. Lower it gently as to not hurt the oil pressure sender below it. Remove the nuts holding the bracket to the motor. I prefer to use E or external torx bits to remove the studs. Be wary that there are washers behind the bracket and you may lose them or the spacers if not careful. Once the studs are out, the bracket comes off easily and the pulley is easy to replace.
My preference is Dayco or another metal pulley of the correct size.
00 Regal GS: All kinds of cool stuff.