This may be a long shot but by what you said in your question I take it the installation is run as a console application (else you'd have to explain what you meant by "get the output"). If you want to capture console output when running a remote process you might consider using Mark Russinovich's Sysinternal Tool
PsExec[
^] command. It will let you run a command on a remote machine while dumping the output of the process on your local PC. You'll need sufficient rights though to do that, but PsExec lets you pass user and password in its invokation.
I have done stuff like that with PsExec before, but must admit it was on a LAN in a subnet, so I didn't have any issues with firewalls. Your results may vary :).
Best of luck!