changing a tub to a shower

Has anyone here taken out their "bathtub" and replaced it with a shower pan ?
I was having trouble with a soft spot in our bathtub.
I finally took out the tub to support it better and found floor rot.
It seems to be from clearance lights filling with water and running back into the wall.
After repairing the floor, I am thinking about replacing with a shower pan. I was wondering if anyone who had done it had any tips ?
It looks like a straight forward swap. Any suggestions on where to buy it ?
TIA