Medical places will always send you a bill as if your insurance is paying for it, and when they find out that isn't the case, they will immediately reduce the bill if you call them. My daughter had to go to the hospital when I was laid off and the bill was $2400. I called and told them the situation, they immediately knocked it down to $1600, no qualms whatsoever.
I know you feel like doing 'the right thing', but the right thing is for you not to be charged if you went to a place that took your insurance. Call the receiving dep't, and tell them what you are willing to pay (as suggested earlier, as if your insurance covered it), and if they don't accept that you really should consider letting it go to collections. It gives you more bargaining power and I can show you how to get it off of your credit score later. There has been some really good advice in this thread so far.