So now that you built your package you want to put some nice message during its installation...
shell script in the postinstall? Naaahh... it's highly deprecated... debconf is what you're looking for.
debconf is not that complicated thing as debuild is. Clicking the link you get most of the stuff explained.
Just a couple of things:
* remember to declare every variable you use in your templates file
* remember to put dh_installdebconf in your rules file
* if you really want to display that info message that you really want to display put Type: note
