Weed Eater One

Hi, how are you?
I need to buy this part: #428876
It´s for the Weed Eater One WE261

I would like to know:
1. How much it costs?
2. Do you ship to argentina? What´s the cost?
3. That number of part represents all the differential asm? Just the plastic disc? just the steel stick?
4. How can I pay for that part?

Thank you so much.
I´ll be waiting your reply.