Yeah...don't think this is the least bit true. Various interviews and other sources over the years stated that, due to Maren Jensen's unavailability (or unsuitability) to play the role of Athena, the Season 2 premiere (had it been filmed) would have had Galactica come under attack and Athena near-mortally injured. She was to have reconstructive surgery to save her life, but allowing Jensen to be replaced with another actress. I have never heard of a sex-change subplot, as a rumor or otherwise. Remember, this was late-70's, early 80's quasi-kiddie-timeslot programming, back when the networks were still in mortal fear of the standards & practices censorship machine - the same timeslot and censorship that killed Galactica 1980.
A sex-change thing never
would have happened back then in a show like that.