2002 Mercury Villager Engine Gasket

Local firestone facility has recommended that I replace engine gasket, rear main bearing seal set, oil pan set, replace main bearing oil seal and replace engine oil pan and or gasket for approximately $1,000.00. I have no visible evidence of oil on garage floor. They have noticed oil buildup on block. I am of the opinion to at least wait until I have visible evidence of oil dripping and recognize that sooner or later i will have to replace these parts but would prefer to wait. What do you think? I believe that this is a 6 cylinder but could be wrong.;