How long it takes to get your green card after the interview ?

hello i came to USA in December 2008 i got married to US CITIZEN then i applied for the green card i sent all the doents on may 27 2009 i got my work authorization card in august and my travel doents , and today 19 august they sent me the request for the interview will be in September 14 , our marriage is so legit we have pictures doents shows all about joint account and bills affidavit of support taxes return year and w2 ,,,,,, so we are ready for this interview but i wanna know when they will probably give me the green card if i be approved for it and if i got approved can i go take a vacation to my country and still came back just with L512L and my pport and the green card approval papers or i have to wait till i get the green card on hand please anyone who has any information let me know i wanna know if i need anything for the interview to take with me and how long it takes to get ?