It is not a sale. Technically, the trust acquires the interest from the decedent and, as per Section 1014, that generally results in the acquirer (the trust in this instance) taking a stepped up basis. Income would be allocated based upon the date of the decedent's death.
Again, this is way beyond a DIY scenario as has been mentioned several times in this thread. Please seek guidance, in person, from a local tax and/or legal professional.
