update: yes, i did end up using the ground and constant from the stock amp. the constant is the orange wire (maybe with yellow stripe? its the only orange one.) and the ground is the black wire (again, i think with yellow stripe, right next to the orange wire).
for the switched lead, there is an empty fuse slot in the passenger fuse box. if you are looking at the box from the drivers seat, the box will be 2 rows tall and much wider (maybe 7-10 fuses wide). anyway, the bottom right fuse (looking at it this way) is unused. the slot for that fuse that is closest to the driver is the switched side.
