is there a specific requirement for international flights in terms of hours, having an ATP, etc?
i know you need the radio license for ICAO, but anything else needed for me to get my Hawker across the pond in the fall?

Go to FAA.gov and there is a list of things u need in order to fly internationally. Also call your local FSDO and they will send you the appropiate paperwork

If you a new comer to the international scene. Then I would recomend using a profesional Flight planning service, like Jeppesen, or Universal. They'll help you cover all the bases from Foreign country rules and regs to providing Wx, Fuel, and handling services at those locations. Also you'll need various permits, time slots, ATC services and etc. In other words have a professional service help and also a professional pilot who's been there and done that. The penalties involved for violations can be severe fines, A/C confiscation, and imprisonment.