But first, how I happened to see this film.
I have put on youtube an example payoff from the film. In this sequence the crew of the TV series think they are trying to join their colleague for some sort of paid fan experience, or job. They think these geeky looking "Thermians" are just badly adjusted fans of the TV series.
While we are on the subject of Galaxyquest, here is a link to a post by Ken Perlin in which he discusses a way to quantitatively rate a movie which is based on his experience of first seeing Galaxyquest. His post is not about setup and payoff per se, its about the bigger questions that this movie raises.