An update- I disconnected the battery this afternoon to see if resetting the ecu would help, the thought being to try easy things first. When I started it after reconnecting the battery, it fired right up and was fine. However, when I started it to go to class this evening, it stumbled again before catching and idling properly. The car upshifted fine, but one time I let up on the gas and it stumbled as the revs dropped. On my way home, as the car warmed up it stumbled big time then caught again <_< (it was in gear, so that should rule out the tranny). At this point, my guess would be some kind of sensor, perhaps O2? To wrap it up, whatever is wrong causes it to stumble upon startup, at one spot while warming up, and when upshifting under power. Any help is (and has been) greatly appreciated!