2. Have you already called them and if so, what did they say? If not, don't call them yet.
3. Cally insurance company first and ask them what you should do. Since this was started by an accident, you will need to take direction from them, regardless of weather the accident was your fault or not. By bringing them into the loop early on, you remove any issues of them denying you coverage or payment for any damages, regardless of who caused it or for what reason. BE SURE TO DOCUMENT THIS....NAME OF THE PERSON, TIME CALLED, ETC.) sorry for yelling....
Depending on what your insurance company says, you may be left with several options. Hopefully, the accident was not your fault and your insurancde company is already dealing with the at-fault person's insurance company. More than likely, your now-blown center diff will be covered regardless of who is at fault, but it sounds like it might have been a fairly minor accident, and thus, your insurance company may question as to why you are in need of a new tranny/center/front diff assembley (all pretty much on unit).
Be patient and polite no matter who you talk to for whatever reason. Start a log NOW and document each phone call date and time, who you spoke to, and the particulars of the discussion. This could be invaluable later on if anyone starts the run-around on you.
good luck, and keep us posted.