I'm a little late here but I just wanted to say I'm glad to have you with us. Sorry to hear about the bad experience you had with (ex-)GF. I can see how having an open arrangement might aggravate more fears than a closed arrangment. I myself am in a poly unit that is basically closed, and enjoy the "cage of protection." I especially like not having to worry about STI's!
I'm sure as you continue to read (and post) you'll get a better idea what to expect, what to prepare for and how. Being prepared helps us to overcome fear.
Wishing you the best of luck and love,
Love means never having to say, "Put down that meat cleaver!"