Need detailed help on creating a Debian package (post-install configuration)

[T o n g <mlist4suntong@yahoo.com>]

Hi, 

The Debian package that I'm trying to create is libpam-ssh-agent
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=595817

I need it to rsync files that belong to root between two systems as a 
normal unprivileged user, without specifying password (the root account 
is locked on both of systems, details at 
http://superuser.com/questions/605425/rsync-root-files-between-systems-
without-specifying-password). 

I've successfully built a package, the building and installation was 
fine. The problem is that when people use Debian packages, they tend to 
assume that the package will work out of the box, whereas this pam-ssh-
agent-auth PAM module need a bit of post-install configuration before it 
can be used, which I found at
http://www.evans.io/posts/ssh-agent-for-sudo-authentication/

I.e., it need to configure 3 system files, /etc/sudoers, /etc/pam.d/sudo, 
and /etc/ssh/sudo_authorized_keys.

I've trying to automate the configuration as much as possible and have 
created patch files for /etc/sudoers, and /etc/pam.d/sudo:

etc/sudoers: http://paste.debian.net/12646/
/etc/pam.d/sudo: http://paste.debian.net/12647/

However, that's pretty much all that I know/can do. I don't know what's 
the Debian policy regarding altering system files, i.e., is it OK to use 
my patch files, and if yes, how to automate it in Debian package post-
install configuration.

Please help. details are appreciated. 

Thanks