After some more work, I finally got the seats out. The drivers seat came out without an issue - there was a pin on it, but it didn't catch on anything. This led me to believe the pin is used for vehicle assembly and is not meant to be a fastener, so I cut the pin on the passenger seat using a reciprocating saw. So far, this hasn't resulted in any problems, and the seat goes back in without an issue. All other posts I've found suggest that the seat should come out easily after you take the bolts out, so I assume my seat's assembly pin being caught on something was just a fluke.