Nope

how do i finalize the sale of the asset? Do I have to enter the sale date somewhere?

The asset was sold the date that the installment sale began.  The taxpayer has just been acting as a bank since that date.

How does the program recapture prior depreciation in this process? It was a rental on Schedule E for prior years

That all should have been factored into the first year of the installment sale

If you have a little magic marker, then check Box G in the first smart sheet section of the 6252.  But then you have to wash your screen so just use an x there.