First of all, have you updated the tablet to the 2006 OS? If not, you really should. That adds a proper package manager, among other things, which will simplify your life a lot.

Once you run the 2006 OS, you just add the software repository address in the Application Manager. For the GPE calendar etc, the info is:

Repository: http://downloads.kernelconcepts.de/maemo2
Distribution: mistral
Component: free

Then, when you select to install, say, the calendar, the application manager will figure out the dependencies and install the required extra sub-packages. There are quite a few when you get the GPE apps.