Should I have filed for an extension? I did. waiting for AGI for 2017 from IRS.. Do I leave my return where it is at and finish when I get the AGI information?

[PaulC1]

Yes, but crucially - if you expect your final return to show that you owe money to the IRS and/or a state tax agency, you need to pay most or all of the amount due by the 4/15 deadline in order to avoid interest and penalties. If you will get a refund, you actually didn't even need to file an extension (but it's harmless to do so!).