the Gene Cash apps are not compatible with N810 and most likely not compatible with OS2008 in general (I could be wrong on the 2nd part).

For a nice place to go to for apps (including GPE calender, contacts, etc) Go here: http://maemo.org/downloads/OS2008 . The gronmayer page listed in the op is great for downloading a bunch of repositories all at once or looking for a particular package. I use maemo.org for general browsing through available apps.

Please don't be alarmed if when you try to download/install an app right now if you get error messages and have a hard time. Maemo Extras is the repository with a lot of cools apps in it but it's not working well right now. However, it appears that GPE suite is not in that repository so you should be able to grab it.