Question for swingers only!?

My bf and i are both 20 and have been together for four and a half years and the idea of swinging kinda turns me on and my bf i know is into the idea of a threesome but i don't think thats as fair lol so my question is will it hurt our relationship if we're both up for it? and what are some things we can expect as first timers? just some advice would be helpful should we or shouldn't we? any tips?