Your cell phone related questions are already covered - most any bluetooth-enabled phone should work, and depending on your plan you may either need a special data option (usually around $20/month), or be charged per minute or per kilobyte (which can run up quickly).

However, if you already have a wireless router at your house, you should be able to immediately use it with the N800. The setup is probably very similar to your notebook (i.e., if you use encryption on the wireless network (which is recommended), you'll have to enter the encryption key on the N800).