User Activity

I have listed 40 or so items on eBay.co.uk and an American is interested in one of them but says 39 of my items are visible on the American site but this particular one isn't. What do I do to ensure it is available on eBay.com?Thanks
I kkep getting this message "Sell faster by sharing your item". What exactly does this involve (I'm not on twitter or facebook) and is it worth it?
I am in the UK and have sold an item to someone in the US. She wants me to invoice her through PayPal for the book and tracked & signed for, rather than use the GSP option. How do I do this, if indeed I can.