What's the best way to negotiate a severance package? Should I hire a labor lawyer?

Should the labor lawyer be at a meeting with me to handle the negotiations? Or do I just get the advice from them and negotiate myself. I am on FMLA and my company on week 4 out of 16 weeks and they called to tell me that my position has been terminated. The labor department in my state told me that the company is in violation because they should have waited until the end of my FMLA leave. I want to use that as leverage to increase my severance package but wanted to hear from labor lawyers if I should do it myself or go in with a lawyer.