I've had a recent experience in which I sold two of my basses to a buyer in the UK. It was my first attempt and it worked fairly well, but I don't think I'll do it again, because:
1) Shipping can be very expensive. UPS wanted to charge me roughly $400 minimum. I ended up using USPS (Postal service), but the delivery time was 4 - 6 weeks. There is a tracking option, but that also raises the price considerably.
2) As far as paperwork, there isn't much. Mostly the normal stuff, plus a declaration of the value of the instrument. Duties are paid by the buyer at the receiving end, unless you have a different agreement beforehand.
3) Finally, since you're dealing with an international geographic/legal jurisdiction, you may have other complications, such as time zones, not to mention the sheer distance, which may complicate matters if the sale goes awry, god forbid.
I've done over 100 successful transactions on eBay and have found that there are plenty of buyers in the US and Canada to provide an adequate client base.
Better yet, sell it on TalkBass. Then you got a better chance to get the bass back if you ever regret having sold it!
