If you want to create a *perfect* backup of your drive, use "dd", and copy the dumps to your server:
$ sudo dd if=/dev/hda1 of=hda1-backup-$(date).dd.img
$ scp hda1-backup-$(date).dd.img user@server:/dir/to/store/disk/image
If anything goes wrong with the install, you can just reverse the dd command to dump the image back onto the partition you got it from.
PS. Depending on how long "many years" is, Debian installations are significantly easier than they were 5 years ago.