1) The typical documentation for taking camera gear into foreign countries is the carnet. However – not all countries accept the carnet (Mexico is a notable example of a country that doesn’t). Check at atacarnet.com for carnet info. Basically a carnet ensures a foreign country that gear you bring into the country you will bring out again.
2) Work rules vary by country. On a recent trip to India we had to hire a local from the tourism department to accompany us. Check with the country. You may need business or media visas rather than tourist visas – and that may come with additional requirements.
3) I wouldn’t deal with transformers to convert the power for your lights. Good ones can be bulky, fickle, and expensive. Instead, just get 220-240v lamps for your lights. That, and a plug adapter on the cable and you’re good to go. Although I use Arris and Kinos at home, I travel with Lowel Omnis and Totas. Foreign voltage lamps are readily available, and they’re light to pack (important in these days of reduced baggage allowances). If you want more involved lighting gear, seriously consider renting locally.
Bring more plug adapters than you think you’ll need. And double check that your battery charger is dual voltage. And bring extra fuses for the charger, and even an extra charger if you have one. I’ve had voltage spikes fry a charger.
4) Lets see….passport, visas, power stuff… You might want to do a little research online, and put together a list of rental houses, freelancers, and supply houses in the cities where you’ll be shooting. If something goes south (and, given enough time, it will) you’ll have a priceless list of resources you can call on. You’ll be the hero! Good luck, and have fun.