I think males are usually sexually mature around 8 months. You can tell when they are going through puberty when the bald spots forms. From my understanding females are sexually mature later in life. I think around a year old. Might want to fact check me on that.
Will they fight? That depends on the gliders themselves. Some gliders get along fast, other don't. In some cases they never get along. Males and females tend to get along pretty well. Females tend to get along pretty well.I personally find female pairs to be easier to take care of. Two males tend to have a few more problems because they can get territorial and dominate. But all in all it really just depends on the gliders' personalities.
I've had Joeys and they are a lot of work and can cause lots of heart ache. I wasn't the one to buy any of the gliders; if I was I would never have gotten the male. Makes life and sugar glider owning complicated. They have one or two joeys about every six months which adds up quickly. In the two years since we got the male I've had nine gliders. We started with three (two females one male). I've since neutered all of my gliders because of it. I currently have seven and I don't want to add to that anymore. (Two did pass away)
I just wanted to let you know a bit about the hardships of breeding. I wish someone told my brother about it before he received the male so he could have planned accordingly.