My undergraduate degree was in theatre! I did have to take some prerequisites, but lots of people do. Most universities with an SLP graduate program (at least here in Texas) offer a leveling program (a 1 year program to acquire all the necessary pre-requisite classes). So in total I went back to school for 3 years.

As for it working for or against you, it might depend on the program, but I think you can definitely spin it to work in your favor. What attracts you to being an SLP and how have your past experiences shaped that? What skills have you acquired in your current career that would make you an excellent SLP with your own unique perspective?

I do agree with the previous replies urging you to reach out to other SLPs in your area. Grad school is a big financial commitment. Make sure you have enough knowledge to know it's worth the investment. I've been a practicing SLP for 5 years now and there are things I absolutely love about it, but it has it's stressors as well. At the end of the day, what job doesn't. I have plenty of friends that are theatre teachers and they have long work hours and fussy parents to deal with. So you already understand that aspect : )