Inherited Network Administration Responsibilities. Guidance please?

Our current network administrator has moved on to another employment opportunity. Her responsibilities have been distributed among the remaining employees; I have been charged with administrating the network.

This individual subscribed heavily to the philosophy that keeping information to herself translated to job security; a philosophy proven flawed by the fact that she was "compelled to move on".

So now I'm faced with the challenge of trying to make sense of this network; cable paths, device locations and router configurations, just to name some. Among the issues is trying to locate a DNS server which has an address on the subnet but I am physically unable to locate.

What I am asking is this: How would you approach this situation? Given the responsibility to take over a network which was previously administrated by someone else, how would you approach assuming the administration responsibilities, when the previous administrator moved along without passing along information before leaving?

Thank you in advance.

Take a complete inventory of all hardware in the network, including MAC addresses and IP addresses (if not being assigned via DHCP). While you are doing that, make a diagram of the cable routing so you'll know where the CAT-5e (or 6, or fiber, or whatever is being used) is located. Keep good notes while you are doing this, and then compile everything into a spreadsheet/word document; print out a copy and put it in a binder, and let your boss/coworkers know where the binder is located and where the electronic document is located. If you do these steps, you'll find your missing DNS server.

If you have little practical experience with network administration, ask your boss to send you to a few training classes for network administration. If he can't afford to do that, hit your local library/google/whatever and start reading about how to manage a network.