A: The real question is, is there any probate left in the decedent, (testator)'s name alone on his date of death? If so, the will should probably be probated. You need to retain independent counsel to determine whether the will should be "probated" or not.
A: You need to retain counsel to look at all the facts. In Missouri, a will is only effective on the date of death (testamentary) over property left in the decedent's name alone on the date of death. Arguably if the parents quit claimed it to you they didn't mean to leave it subject to the will. The question is what is the nature of the "oral contract"?