Okay, I have been looking at the bathroom and have remodeled it in my mind. Time to start asking questions about what I need to put this into reality. I have a basement bathroom that has poured concrete walls and linoleum on the floor. There is a teeny tiny itty bitty prefab shower and I want to put in a larger shower. I had thought about prefab but since I want to use the existing drain, I have decided to try to do a mortar base and tile. I haven't taken the existing shower out yet so I may be in for more surprises when I do but my initial question is what will I need to do in order to be able to tile the concrete walls? Would applying Kerdi around this make it an "easier" project?

Kerdi is definitely an option. By far the easiest solution is to re-locate the drain and use a pre-fab unit. However, if you're set on tiling consider a Schluter shower kit or a liquid waterproofing membrane like Aquadefense. Use a Schluter drain unit regardless. Read a lot first and then decide. You should know that a custom shower with pan, niches, etc takes a professional setter about a week to complete. For a DIY project you should allot about two weeks. This is what makes moving the drain so simple by comparison.