How to remove and replace old shower pan and drain

[Jrew]

I’m looking to totally renovate my bathroom with my handy father. I’ve slowly demolished the shower wall but got stuck with the shower floor, which coincidentally enough is a big reason for the remodel. Seems I'm told that lead was poured between the floor and drain being that this was probably done in the 60s. I’m looking for advice on how to remove the flooring while trying to maintain the drain intact if at all possible.
Thanks