Well, the pins of the connector seem to be described well. Seems like regular RS232 is available - good old serial port.
Software - RS232 can be handled using any terminal emulator. Putty, Hyperterminal, RealTerm - all can do it.
And the protocol - if it isn't described in the documents you have, then you will either need to google more or reverse engineer it. It is fairly likely it is going to be something ASCII text based, though.
However, you may not be able to get the actual received data over RS232 - that signal is on the maintenance connector, so it is possible you will have only diagnostics/service info there and the data are available only through RS-422/485. Nothing a microcontroller with a receiver chip couldn't handle, though.
There is also audio output there - that would be probably the first thing to connect to make sure you are actually receiving anything to begin with.
You will likely have to make your own cable based on those documents unless you can source an original one somewhere (but then it is likely to have a normal serial port which today's PCs don't have).