Pura Vida dive shop is a little to the east of the park, and Force E is a little west of the park either is fine for tanks and weights (I am partial to Pura Vida myself). BHB is a relatively easy dive there is some current to deal with, but nothing that is going to sweep you a long distance away. Google Blue Heron Bridge dive and you will find some good explanations on how to dive it. However, both shops have dive guides and
@Scuba_Jenny who is often on this thread is well respected as a guide.
Using a dive guide for your first dive flattens the learning curve, makes it easier to not waste time figuring things out for yourself, and are great for pointing out fish and critters you might not find yourself.