This is not easy, frankly, and TurboTax does not make it any less so.
The bottom line is you need to convert the relinquished property to personal use for no purpose other than to stop the program from calculating depreciation deductions throughout the rest of the tax year.
If you're electing out, you want the depreciation to stop on the date it was taken out of service (which should be the same date as the replacement property was placed in service).
