Styrene base over old tile floor?

I have an old tile shower that was leaking and was going to put a new enclosed styrene unit in instead.

I'm kind of scared to start jackhammering to remove the base - won't I crack the drainpipe? Would it be OK (or wiser) to leave the old floor in place, extend the drainpipe upwards and put the new syrene floor above it?

Parry

Tear it out. Check over at www.johnbridge.com for tiling info...lots of traffic and many tile pros. Personally, I prefer a tiled base. Once you understand the method, it isn't that hard to do.