How was the aftermarket radio wired?
Did it have a plug-n-play harness, or did this involve cutting wires?
Did any wire accidentally ground out? Any sparks?
I would start with the 125A maxi fuse in the front of the fuse box and do what Mooseman suggested, start checking fuses, both the underhood fuse box and under the LR seat.
Hopefully you didn't get a short and damage the BCM.