E36 cooling system,do the whole lot or dont bother

the m50 and m52 engines overheat and warp heads. dont just replace the part that failed. do the expansion tank, all hoses, thermostat, water pump, and aux fan switch in one go. the plastic components all age at the same rate and if one has gone the rest are right behind it. budget about $500 in parts and an afternoon. way cheaper than a head gasket at $2500.