You can see almost1 all the files of an installed package by running
dpkg -L thatpackage
Or this same information is available on http://packages.debian.org — you pick a package in the required distribution, then on that package's page navigate the "file list""list of files" link in a table row matching your hardware architecture.
Another package which might be of interest for you is debsums which is able to compare the files belonging to a package or a set of packages, as found on the filesystem, with their MD5 hash sums as recorded in the metadata of the packages. The intended usage is detection of tampering with the system files, but might be used in your case as well, I think.
1 Some packages create certain files and directories dynamically, and unfortunately this is not declarative: they do so using plain shell scripting in the so-called postinst and postrm scripts, which are called by the package manager when certain events happen in the package's lifetime. For instance, a package might generate its configuration file using ucf from a privately-kept template using the information obtained from the user during the package configuration phase, and install the generated file somewhere under the /etc hierarchy.
These "plumbing" scripts belonging to a package are kept under the /var/lib/dpkg/info hierarchy and have names matching the packagename.* pattern. By the way, the lists of the files installed by a package and the list of configuration files maintained by the package are kept under the same hierarchy in the files named like packagename.list and packagename.conffiles. This is an implementation detail (better use dpkg -L or similar devices) but still…