I read an article recently where the author said, "Most of us spend too much time and energy trying to hide our fool-hood." By this, he meant that we spend too much time pretending to be something that we're not.
That's an interesting concept. A lot of us try to be experts in our field ... and are afraid we'll look like a fool if we ask our client to clarify something that is probably basic to them. I've tried to be better about this -- by telling the client, "I know a little bit about a lot of different fields, but I'm going to rely on you to help me understand enough of what you do to create a resume that will get you interviews."
Right up front, I'm giving myself permission to look foolish to this client. And you know what? Not one client has objected. (I thought for sure one of the first ones I said this to would come back with something like, "Well, what am I paying you for then?" Nope, that was just foolish thinking on my part!)
Afraid of writing for a new field? Be willing to be a fool! Take risks, experiment with new skills ... grow! The rewards are expanded creativity, more joy ... and a potential new market.