Do I need to include the sale of an inherited farm land contract on property received in 2017 that was sold on land contract in 2012 in Turbo Tax for my 2017 return?

If you are saying the land contract was completed and deeded over to the buyer in 2017 before you inherited it, then you do not need to report it. (You said that all capital gains have been paid or is that "so far").

If the land contract is ongoing and has not been completed and deeded to the buyer yet, then you do need to report the capital gain on the installment sale on your 1/3 of the property.  You do receive a stepped up basis, however, which will help reduce the capital gain: use 1/3 of the stepped up basis as the cost to subtract from your portion of installment sale to arrive at the capital gain.

The basis of property inherited from a decedent is generally one of the following:

• The fair market value (FMV) of the property on the date of the decedent's death.
• The FMV of the property on the alternate valuation date if the executor of the estate chooses to use the alternate valuation. 

Can you provide the IRS information that backs up the stepped up basis? I thought since the land contract was established before date of death there is no stepped up basis.