I have an existing sink in the bathroom,, I'd like to take the sink and vanity out and install a shower in it's place,, how do I transform sink plumbing into shower plumbing??

how do I transform sink plumbing into shower plumbing??
You remove the sanitary tee and stubout and replace with a piece of pipe. This will make thie vertical pipe the shower vent. Now open up the floor and cut a 2"wye or a 2" combination wye and eighth bend in the lavatory drain line and run over to a trap and raiser directly below your shower drain. You may pipe the water over from the lavatory supplies. Good luck, Tom