Q. Does passing wind while I am showering break ghusal? Does one have to step out of the shower, and then come back into the shower to make a fresh ghusal?

A. If ghusal was made, and all the Fard (compulsory actions) of ghusal were complete, then all one needs to do is make a fresh wuzu. If wudu was broken whilst in the shower after the ghusal had taken place, one need not step out of it. Merely continue by making a fresh wuzu.

Passing wind, (flow of blood, urine, etc) negates wudu, it does not negate ghusal.

Had you not completed your ghusal and passed wind, then in such a situation you would have to continue with making your ghusal.

It is preferred that Wudu be made before one makes ghusal. However, wuzu would be done after the ghusal, as in the case of a person who broke their wuzu after the ghusal had taken place.

Allah Certainly Knows Best.