If you mess up the modding which you should not do if you read the tutorials correct, but if you do then these can be fixed depending on what drive you have if the only thing you do right is make a safe backup of your original.bin
So you should not have to buy a new drive.
Take your time reading this tutorial until you are ready to go ahead with the modding if you have any doubt don't do it.
http://www.360mods.net/Downloads/details/id=61.html
Regards
X5