Get your taxes done using TurboTax

First ... even if you are holding payments on the sold items you can enter the full sale this year on the form 4797 and only the interest in future years.  So review the return as it stands and see if this may be an option you would like to take.  SAVE the return under a specific file name so you can return to it later if you choose this option later.

Now you did everything correct up to the point where the program asks if you sold this as an installment sale ... edit your assets and say YES for each of them. 

It may be easier to either do this in the FORMS mode  or   indicate that all of the assets were taken out of service to stop any depreciation  and then make one entry in the 6252 section ...