You have at least two options that I can think of, neither of which are ideal. To start, you could search on CCO for the password recovery procedure. This involves overwriting the existing config file. The first time that you boot after that, the router will prompt you to enter config mode. This allows very basic setup from an interactive prompt. Can't say for sure if it is enough to get you going but it probably would be. Second, there is Router Software Loader (RSL). I am not a big fan of this either, but it seems to be more functional than the aforementioned config mode. You will need all of the passwords to use RSL, so you may need to do the password recovery procedure either way if your customer didn't provide them.
Here is a link for RSL. There is a hotlink to the download site a page or two down from the top.
Good luck.
http://www.cisco.com/warp/public/779/smbiz/service/knowledge/general/rsl.htm