... coolant you may not have an issue at all.
What seems to have happened, according to your description, is that the coolant vented due to air in the system.
The one issue I would look for is for any coolant under the rear trunk carpet.
If it's wet, then you need to replace the coolant reservoir.
If it's dry, take a look at your coolant cap's part number. If the last 2 digits are 00, 01 or 02 go to the dealer and buy a new one.
To refill your coolant system, you can follow these instructions.
http://www.pedrosgarage.com/Site_3/Install_3rd_Radiator_%26_Coolant_System_Bleeding_I nstructions.html
Go about half way down the page to find the coolant air bleeding instructions.
Happy Boxstering,
Pedro