there are several great electrical contractors out there that can help you, but make sure that they're licensed and insured. everybody thinks that they're electricians, but i sure wouldn't risk my family's safety by using someone that isn't licensed and insured. if you decide that you want to do it yourself, i would be happy to give you some pointers on how to get it done. it's legal in texas for homeowners to do their own electrical work (along with plumbing, etc), and being that you're the one living there, there is a pretty good chance that you'll make sure that everything is done safely and correctly.
if you can access the area above your shower in the attic, it makes it fairly simple...espcially with "remodel cans"...you just cut the hole in the ceiling and the light slides into place from below. you can run a 12/2 romex from an existing switch (or add another) to the first can light and loop them from there.
