Possibly Star Fall by David Bischoff from 1980?
The space traveling cruise ship certainly matches (though it was interstellar vs. inter-galactic). So does the body swapping (snippet below).
If it is Star Fall then it appears to be a duplicate of the following: Brain swapping, alien conspiracy, space cruise
It reads like the author wanted to do some musing on the mind-body connection, so he just straightforwardly incorporated that into the story before there was even a story. We’re introduced to two characters – Philip Amber and Todd Spigot – who are opposites physically and mentally and, through circumstances that aren’t that well-explained and clearly there for the convenience of the plot, end up having their brains implanted in bodies that belong to the other. Note the wording there – it isn’t clear that the body that Philip Amber starts the story in is his original. He seems to have been doing the manner of body-hopping for a long time. Todd Spigot’s body is the one he was born with, though, and one of the more interesting points in the book is the changes it goes through while inhabited by a fitter mind. As the story progresses, we run the rest of the gamut – there are disembodied brains, cyborgs, collective minds, and human-alien hybrids.