I have used WD-40 for years when cleaning antique guns without any harmful effects. That said, I also leave them untouched if at all possible and aside from flipping the wedge over I wouldn't do anything to that revolver. I do recommend being careful to make sure any oil only gets on the metal parts and not the wood, but that shouldn't be a problem with fixing your wedge issue.
I know it sounds backwards, but one piece of advise I would give you with the strongest recommendation is to never let a professional gunsmith touch any of your antique guns! The reason is simple, there is no way of knowing what they will do it with it. I'm sure there are a great many good ones out there, but anybody can call themselves a gunsmith, and even the good ones are mostly used to working on modern, working firearms that don't have collectible value. There are no shortage of horror stories out there that are the result of a gunsmith doing something that was never asked for by the customer. In my case, it was an idiot who decided to "clean up the rough spots on the barrel" for me, without asking, and polished off the proof marks!