I'm now trying to create Cydia package.
Most of the packages I plan to do are fixes for my country -
e.g. the "like" 5.99$ proxy solution (to allow browsing through WAP), AppSupport & Carrier Settings for my country, etc...

When creating Installer package you simply "script" the entire process.
So for example if I overwrite a file (eg preferences.plist) I can copy it first to backup it.

Does Cydia does that automatically? how can I Install/Uninstall when most of my packages overwrite files in order to mod them.

And another question (a little OT),
How can I get my source add to Cydia. not manually but within Cydia itself. who should I contact?