Can't help because I've got the wrong set of tackle...
But I just wanted to say good luck, mate. Be careful and take your time. If it were me, I wouldn't jump into a situation where you feel compelled to act out your fantasy.
Wouldn't it be better to seek out a Gay/Bi venue and just go and chat with the guys before arranging a meet for the intent of sexual contact?
Don't forget, you aren't just taking your first steps into the swinging arena, you're taking your first steps into a whole new sexuality.
Best
Hxx
Try
There are plenty of guys like yourself on there, each with a profile. You can contact through an online messaging service or via an email system.
Get chatting to guys first and take it slow, social meets are better than going to just have sex. It is far better to get to know a prospective partner first no matter how short-term your liaison is going to be.
Easyhorn - where are you located? If in the North I can suggest just the place for you! Liaisons, Rochdale run a bi night alternative Tuesday evenings. It's very relaxed and you can just watch if that's as far as you want to go for a first time. Sounds like a reasonable place to start to me!