If you didn't get a user manual with it, download one from the Canon website and refer to it so you know all the controls. That will help you checking out the camera thoroughly.
It would be nice to get all the originally bundled accessories besides the instruction manual, too. Those would include a battery, strap, a body cap, cable to connect the camera to a computer. If you haven't had a previous Canon DSLR, it would be nice to get the original software disk too... It is out of date now, but to install updates downloaded from the Canon website, you need to have an earlier version installed (it is possible to install it without that, just not as easy... if you need to do so, search here or elsewhere on the web for info on how to do it).
Once the camera is yours, you might check the firmware version installed on it and, if needed and if you wish, update with a download from the Canon website.
5DII are pretty durable and problem free. It's rated for 150K clicks, so that one is barely broken in. I'm sure you'll enjoy it!