to all sifus,im new in this motoring industry.. bought a 2nd hand with 90xxx mileage.. my questions are. when is the time to top overhaul and when is the time to do full overhaul? is there any sign? what is the cost for top overhaul? and how about overhaul? what parts are replaced on top overhaul and overhaul? hope all sifus here can answer my question. newbie here needs some knowledge