You can estimate shipping at http://postcalc.usps.com/
You need from and to zip codes and the weight of the package. Looks like it would be about 8 ounces. But to be sure, use a kitchen scale or take the package to the produce section of the grocery store.
You can print postage straight from paypal (if buyer marks payment goods and includes shipping address) for items under 13 oz or for flat rate boxes/envelopes above 13 ounces.