Goodtimes has some good advice there!
I think the two of you are ready to try swinging, but I agree with Goodtimes that it's probably not a good idea to have a MFM with a co-worker (ever!). There is just too much potential for things to go really wrong -- then she'd have to see this dude at work!
I definately think you two are moving in the right direction as a couple. It seems like you have open, honest communication, and that's essential for a good relationship (swinging or not). If you poke around these message boards, you'll find lots of good advice on choosing the right single male for your first MFM. He should be willing to sit down with you both, and talk openly about expectations/ rules, and how to keep everyone comfortable. Communication is just as important in swing partners as it is in your primary relationship.
Good luck to both of you, and we hope to hear more from you and your lady!
Trixie