So I took my car to the dealership, and it stayed with them for 8 hours, with an appointment, only for them to tell me that the transmission hesitation and behavior was normal, which isn't if it wasn't problematic until recently. I also told them about the rattling door panels, and they said they were unable to hear them until I personally drove them in my car...so that'll be fixed whenever I schedule the appointment (the bright side of a rather disappointing yet not surprising visit).