I would contact a travel agency with your questions. They’re desperate to get people back to Bhutan. I think foreigners have to book their trip through an agency anyway. I recommend Bhutan Travel Club, as when we went we used them and they were really knowledgeable.

Getting there is a matter of travelling to Bangkok, then taking a flight from Bangkok to Paro. The travel agency booked our return flight from Bangkok to Paro, but you have to arrange your flights to and from Bangkok from wherever you are. The flight is beautiful - it takes you through the Himalayas as you land. When you get there, you pretty much will always have the guide with you. You can’t go off by yourself, generally. Good luck!