battery warranty....
Yeah, you should be able to take it back to them. Also, if I remember right, they have a little plastic bag or tape, something like that, where they stick your warranty info on the battery. But they put that info in the computer too.
Exhaust manifold bolt.........take one to your local auto parts store and see if they can size it up to yours. The size is M8 (metric). I doubt they have the allen head type, but you may be able to substitute.