all you need is both (original) copies of travel document issued by uscis and a valid mrp passport also the old passport if you have one. at the airport a immigration police will escort you to a different room. i freaked out at first but i guess thats just a routine procedure. what matters the most is you have to have both copies of TD before you leave the country. dont get yourself in trouble by saying 'its been approved someone will mail it to me in nepal'. coz sh!t happens