Well, it was all one big false alarm. My transmission is fine...the mechanic found that my coil packs are malfunctioning, sending sparks all over the place and causing misfires.
A $950 day at the spa for the car (new coil packs, wires, full tuneup and a full-on transmission service/flush) and I'm promised a better than new car with glowing skin and a renewed sense of self. We'll see if the car's as happy as the mechanic's promising.
Thanks for your help guys! Very much appreciated.