My N810 is currently running very slow with too much junk on it, so I'm planning to reflash the operating system on it. Before doing so, I have gpe todo, contacts, and calendar data that I want to backup before reflashing my operating system. Is there an easy way to achieve this? Thanks in advance

You can backup the directory '/home/user/.gpe'. It contains all GPE data.

And moreover you can run the standard backup: Settings -> Backup / restore which will backup data into the /media/mmc2/Backups folder.
Possibly you can backup more application settings in the folder /home/user or e.g /etc/hosts if you have set some special host settings .