2. I have been trying to edit, delete old raids and am using the View Previous GRSS Snapshots.. Now it lets me see old raids, but I can't delete any. If I re-import this snapshot. Then any new values I type simple gets added ontop of allready given DKP...
So what am I doing wrong?
The "Previous Snapshots" is only for re-importing, but like you said, it doesn't replace, it only adds.
To delete past attendance, head to Admin > DKP > Raid Attendance. Click "Edit" next to the offending snapshot, and then click "Delete" at the bottom.