To upgrade your server go to our billing panel (http://billing.spartanhost.net). Once there, login and click on services -> my services -> click on your service -> 'Upgrade/Downgrade' under 'Actions' on the left hand side -> click 'Choose Product' beside the upgrade. You only pay the difference between your current plan and the one you are upgrading to, the difference is then divided by how many days you have left until the end of your billing period. You will then be charged the full price for the upgraded amount of RAM from your next renewal date.
Your server data and IP are not affected during the upgrade process.