People don't understand wills and trusts, and a last-second modification like what you've described kind of indicates that grandma was flying by the seat of her pants.
Property that a person owns himself at his death is subject to his will.
Property that is in a trust is NOT owns personally and NOT subject to a will, unless the trust has some power of appointment thing in it.
That's the first problem.
The second problem is that you can't just write a list of your wishes. A will might refer to a separate document for devises, but the law governing that is complex. Otherwise, the list needs to qualify as a codicil - basically meeting all the requirements of a regular will, but being an amendment.
As a general rule, the estate IS liable for the loan, but that doesn't mean the property passes completely to the heir. Possibly the home needs to be sold and the remainder of the proceeds go to the heir.