Depending on what you are shipping of course, but its pretty easy. You may have to fill out a customs form - basic stuff (from, to, what it is, and the value). Some people put "promotional items" or "manufacturing sample" and leave the value at zero. That's up to you.

No need to use global priority unless its something you need to track.

Paypal is pretty easy from non-us as long as the other party has it as well.