Well, lessee.... You were having car work done when he called... do you have any mechanic's overalls? lol
I think you should wear your most comfortable and favorite clothes so you feel comfortable and familiar with your favorite guy in your favorite place.
I'm so happy for you that you get to see him tomorrow!! You have waited so long for this day to come!! I hope you have a wonderful, warm, connecting session that makes you feel sooo good and that good feeling lasts and lasts.