It's considered bad form to slap DV victims--unless you happen to be a batterer, of course.
Good for you--I'm so glad you called the advocate and that she will go with you to court. They are awesome people--I meet a lot of them in my work, and I'm so thankful they do what they do.
And yes, change the locks. A locksmith can come and do it cheaply--I had mine changed when I moved into my (then) new house, just for added security. They don't even have to install new ones, though if yours are flimsy, it wouldn't hurt to replace them. Make sure all your windows, garage, etc. are secure, too. It's a good idea for any woman living alone, even if she doesn't have an angry abuser out there.