(son of decedent who moved back to decedent's farm and operated it after decedent declared dead made claim in probate estate for farm management fees and reimbursement for farm expenses; doctrines of quantum meruit and unjust enrichment not properly before court and son not entitled to any management fee; son received all crop income, cash rent, FSA payments and proceeds of cattle sales and sale of pickup, used home rent-free and used truck and equipment without charge for five years; son entitled to reimbursement for principal payments on mortgage - which benefited estate).