andlamv, I understand your concern because getting new equipment is very exciting. Purchasing equipment can be frustrating if your order is not going through properly. Purchasing the Xoom is like purchasing a phone. You can either upgrade your current equipment (if your eligible) to the Xoom and receive the discounted two-year cost with a contract extension or add a new line to your account for the Xoom with a two-year cost and contract. The equipment has to be activated on a line to be used.
Additionally, if you want to order the Xoom without adding it to a mobile line on your account, the purchase would have to be full retail price, which is $669.99.
When you log into to your online account via My-Verizon, you will need to choose either upgrade an exciting line or add a new line.