I advise that your dad should get a lawyer to execute the will!
My sister and I were on shaky terms, at best, for many years...and she executed my mother's will over these last 2 years. What WAS left of our relationship is now in shreds never to be recovered. She also got away with about $10K in assets that should have rightfully been split. $5,000 is a small price to pay for my serenity.