Sorry to rain on your parade, but nothing easy about your task. If I had to guess, your line is probably not in that sleeve for its entire length. That sleeve is probably just a protective sleeve for where the pipe comes up through the slab. Suctioning the water with a shop vac should allow you to confirm that. Even if there is a continuous sleeve, the bend would probably make it nearly impossible to pull new copper through. The only possibility I would see would be to send an electricians fish tape through from one end to the other, try to pull pex in with that. Its all very iffy!