nonnotorized will changes, need lawyer? maybe challenged

As a general rule, any changes in a will must be attested in the same manner as the will itself. So, for instance, if a will needs to be witnessed by three persons, then the changes need to be witnessed by three persons (you don't say what jurisdiction you live in, so I can only give general observations on the law here).

Also, as a general rule, if a person dies intestate (without a will), the surviving spouse gets everything -- but that's only if the person dies intestate. If there's a will, then everything gets divided according to the will (the surviving spouse, however, may be allotted a statutory portion of the estate in spite of a will's provisions to the contrary).