"I'm told that it will just suck up the moisture if I do."

If it was the guy who applied the drywall mud who said this, then I would say shower elsewhere. When my shower was out of commission, I had to go to the gym, so having another shower in the same house is a real easy fix.

Drywall mud is a sponge for moisture. Don't use the shower.

Just be careful to not splash water in it. I had to retexture ceiling in my bathroom, it was fine. Maybe hold off 24 hours right before paint and run fan to reduce moisture.

How critical is it to not shower? Wait until it's painted, or use another shower if you really can't wait.

I'd just paint it myself. But that's me.

Should have used greenboard. We put ours up and drywalled mud textured it. No problems

Should have used green board and drywall mud texture it. We did ours no problems and looks good