IRS Pub 537 "Transfer due to death.

The transfer of an installment obligation (other than to a buyer) as a result of the death of the seller isn’t a disposition. Any unreported gain from the installment obligation isn’t treated as gross income to the decedent. No income is reported on the decedent's return due to the transfer. Whoever receives the installment obligation as a result of the seller's death is taxed on the installment payments the same as the seller would have been had the seller lived to receive the payments."

You need to look at the decedent's 6252 to get the proper amounts to show on the 1041. The buyer is just like any of the other heirs, assuming they were not the original purchaser from the decedent.