No, there shouldn't be. However, it is always good to play safe - so make a backup of your DB. I would suggest that you use phpMyAdmin for this.
More info on that and phpMyAdmin is Here
If you have no MODs installed then ift should be a matter of uploading the new files and running the upgrade from 2.0.4 to 2.0.8 and you should be set.
Hope this helps.
Des. . .