To Gypsy: Yes, all you would really need is the battery and the cone if you've got 510 parts. You might eventually want to get an eGo battery charger as supposedly the 510 will work but it takes longer than it would with the eGo specific charger.
Just a thought. I purchased an eGo and forgot about the charger. Having spent my allowed amount (wife's restrictions

) I was stuck on charging my new favorite battery.
If your ok with modding you can take the house charger apart and trim off the plastic that stops the eGo from connecting to the charger. It works for both
batteries then but takes a bit longer to charge the eGo.
Here is a pic to give you an idea.