To unpack all you do is copy the xpak.exe and xpak.bat into your data/packs folder and double click the xpak.bat file. That should then just get on with it and give you folder at data/packs/data with the contents of the .paks in it.

The only thing that won't unpack unless some-one updated it is the patch_0.pak and patch_1.pak. to get them open you need to change the xpak.bat file.
To do that change its name to xpak.txt (ignore windows when it says that will make file unusable) open file in notepad etc and add those file names to the two lines eg:
xpak.exe -mkdir models_building_textures.pak......sprites_0.pak patch_0.pak patch_1.pak
xpak.exe models_building_textures.pak ......sprites_0.pak patch_0.pak patch_1.pak
then re-save it as xpak.bat

Packing something is slightly more complicated but not difficult and you don't often have to do it - post again if that is what you wanted help on.