1: Flashing the tablet is like reformatting your C: drive and reinstalling Windows, except that the tablet's backup functionality is quite good, and you can regain much of your settings and documents by restoring your backup. If you haven't flashed your tablet since you bought it, it is probably running an old version of the OS and you'll want to get it updated (to Diablo 43-7).

2: You don't need to flash your tablet to use Easy Debian. That's why it is "Easy". It lets you use Debian apps inside Maemo.

3: Diablo is the latest version of Maemo (OS 2008). It is officially "dead," in that Nokia will no longer offer updates of this software. Deblet is a bootable version of Debian, and Mer is the community-run replacement for Diablo that incorporates features of the new OS (Fremantle), which won't run on our tablets. Read the Alternatives sticky and the wiki page, too.