I've never read anything to indicate they reproduce asexually; on related subject, according to the Jedi Quest books at least, Muun are at least BORN with hair, as the series featured a Muun child with (IIRC) yellow hair; so apparently they go bald (universally?)
There are female Muuns in Boba Fett: Maze of Deception. Also, along the subject of hair, aside from the reference Sen. Cilghal gives, the Muun Pors Tonith mentions he's got a thing for females with hair and so didn't find Asajj particularly attractive (aside from also being too human). That sort of comment makes me think at least the females have hair. Not to mention some of the statues on Muunilinst in Genndy' show seemed to have hair, although it's hard to tell since the art's more on the stylized side. One of the older Insider issues, which I don't have with me at the moment, had concept art of all the Separatists, including San Hill. He was originally supposed to have hair. IIRC it looked blue.
[image=http://www.geekscribe.com/wp-content/uploads/2008/11/olivia-munn-0220-00-286x300.jpg] [image=http://media.g4tv.com/images/blog/2007/05/25/633156922990845563.jpg] Olivia Munn
I beg to differ. San Hill is a sexy beast. I wouldn't have a picture of him on my desk if that weren't so. And in case you doubt my taste in masculine aesthetics, next to the picture of San Hill is a photo of some hobbits dressed as Agent Smith clones.