If your listing was originally set up using the Quick version of the listing form, then you won't be able to access the options that are only available on the Advanced version (also known as the "business tool"). This includes handling times longer than 3 days.
If you sign up for a "Starter" store, you'll have access to the vacation settings. The minimum commitment for a store is one full calendar month plus the exact number of days remaining in the month when you signed up. So if you sign up in late December, you'll have to pay through January. A full month (January) is $8, and those last few days in December would be another dollar or two.
http://pages.ebay.com/stores/subscriptionterms.html
