I did the same exact thing almost one year ago. It was intimidating because I had not played a tourney in 30 years and little tennis in 20. Wasn't even sure I was at the right level. I mostly practiced my serve before and maybe hit some. What I had to remember was to breathe, relax and not be so anxious. I lost in the first round to a more experienced player but scores were 4 & 3....not too bad. Good luck.
Head, shoulders, knees and toes (knees and toes)....all of it hurts