ok so i was wearing an ncr outfit and ran into a group of legions, they attacked first so i shot back not knowing what was going on, no i am vilified by them, so how do i get back to nuetral status with them? after i killed them it said i failed 3 quest that i havent even started...render unto caesar, kings gambit and another one i cant remember...

You can try not to go around them wearing NCR armour but by the time you are Vilified I doubt theres much you can do.

By the time you get the Chip back Legion may forgive you so Caesar can talk to you.

In Legion land where Legion Armour and don't get to close.

Don't wear NCR armor around Legion, because they will attack and of course your first instinct is to kill them all, and thats how you get vilified.
If I were you i would load up to the point before you killed the Legion troops and change to a non-faction armor so you can do the quests (if you want).
If you don't have a save point before then the only real option to get neutral or better is to wait until you get to The TOPS casino (part of a main story quest) afterwards a Legion man in disguise will talk to you and forgive any crimes against them so far, which allows you to go talk to Caesar, earn his trust, do what he asks you to do, and your reputation will be saved.

Just don't wear NCR armor and don't have Boone as a companion when you enter the fort, you will be shot at.

reload a previous save game?