If you have a repair kit and the leak is easily accessed, I'll recommend DIY. It isn't very difficult. If it is a very slow leak the worst of it will be locating it using soapy water. A thorough cleaning and inspection will usually give you a good idea where the leak is.
As long as this is Hypalon, acetone can be used to remove stubborn stains. Next a bleach gel. Once the bleach is cleaned off plenty of soap and water.