I've demo'd the old shower and walls, the drain pipe is in dirt, rest concrete slab. Should I concrete to the drain pipe prior to a wedi install?

We spoke to our Wedi Rep, and the answer is Yes and no. You need to leave a 6 .in diameter space to accommodate the drain. If you buy the Pan in advance it comes with the drain assembly and a template. You can install prior to cementing, just make sure to wrap the drain in foam to create a gap between the drain and the concrete.