In this episode, we find out Chandler works as an IT procurements manager with the specialization Statistical analysis/factoring and data reconfiguration. He is not a Transponster.
Addressing the question Joey didn't know the answer to: downstage means the part of a stage that is closest to the audience or camera, whereas upstage is the part of a stage that is farthest from the audience or camera.
The shot shown after the first scene with Ross and Rachel has the Twin Towers showing in the upper right corner - unlike earlier episodes in the season, this shot was missed to be taken out of the episode. The Twin Towers showed frequently in shots on Friends before September 11, 2001.
The salesgirl references Ross as Indiana Jones, who is played by Harrison Ford. David Schwimmer and Harrison Ford acted together in Six Days, Seven Nights (1998).