It is complicated, especially if you had boot at the original time of performing the exchange. Assuming that you used TurboTax ( preferably the CD version i.e. everything is on your computer) and that you have continued throught the years to diligently use TurboTax for filing your returns including the rental income --- all you have to do is tell Turbo, the rental property has been disposed off -- it will ask questions and figure out the taxes for you.
If you did not use Tubro through all these years and/or did not enter the exchange details into Turbo at that time, I would suggest go seek professional help and take with you the original QI ( Qualified Intermediary) report of the exchange and the following years of returns -- to make sure that everything tracks.
I have done it i.e. 1031 property disposed off , but I had everything all lined up over the years , but I still had to go over with a spread sheet to make sure I am not missing anything.
Good Luck
