Excellent question Mr Sikey1, you will only have to do the Attunement quest once, and once that is done you may enter the with raid lockdown if you down any single boss from within the attuned raid you are doing.
Nice on the eyes script to verify whether you're attuned - all three quests are completed if you hand in one of them./script local cName=UnitName("player");if IsQuestFlaggedCompleted(9123) then print(cName,"is attuned to Naxx");else print(cName,"is not attuned to Naxx");end