Yes, Form 3115 needs to be filed, which will allow you to enter the 'catch up' depreciation. And you will claim the current-year depreciation as well.
Yes, the additional deduction due to the 'catch up' depreciation could significantly impact your tax return. But rental property usually is a "passive" activity which sometimes limits your current-year deduction, so it is possible some of that deduction will need to be carried forward (depending on your specific circumstances).
I recommend going to a good tax professional this year to do that.
