For 1 thing go to diplomacy, and go to the faction in question and mouse over it. It will say something to the effect of "attack faction xxxx.

This is how you can tell if the A.I. has attacked a faction you contracted them to attack. If it still says attack faction xxx it means the obligation is still there. Along with being able to check if you fulfilled your contract in case you forgot what the deal was made for.

As far as the amount of turns my guess is there are no negative effects if you do it in 10 turns or less. based on senate missions it's 10 turns for all but blockade missions.