I agree that a pro may not be the best to way to go, but who am I to say what is right for you? You did ask for opinions though! I think it may be safer and more fun to go with somebody who is also new at threesomes and figure it out together
Practice makes perfect and it can be fun learning new things-not to mention they won't have slept with as many people as a pro! Also, while I don't believe high end prostitutes at a brothel in Nevada are there against their will, they are there just for $ in most cases-I personally would find it more fun to be with somebody who is just in it for the thrill! There are lots of sites out there now that help swingers and people interested in find sex partners for this very thing! Whatever you decide, just make sure to practice safe sex and get to know whoever you choose to experiment with!!