I've bought and sold from people in many countries, without any issue. As always buy the seller, not the watch, and you should be OK. Don't be afraid to ask for references, then contact those references. Do your diligence, just like any other sale, and you will minimize your risk of a bad deal. If the deal looks too good, it probably is. I'd prefer to use PayPal, but be aware some countries are limited by PayPal on how much the transaction can be. So if the seller tells you you can't use PayPal because of PayPal's rules, don't assume they're feeding you a line because there is truth to that. And PayPal's guarantee is not the same out of the US as it is in the US. So don't assume PayPal will give you the same protection. Most of my international sells / buys over $1K have been by wire transfer. Again, if you're buying the seller this should not be a concern. Be patient once shipped. Unless you're paying for expedited delivery (which is a fortune!) it can be 2 weeks for delivery.
And like Aaron said, factor in the taxes / import cost when making your decision. If you're in the US it's about 4% of the purchase price and the delivery man (USPS, UPS, FedEx, etc.) will collect it from you upon delivery (in the US).
Good luck! It's a great looking watch!!