My Armada Grand bought second hand in 2002 with ODO reading

My Armada Grand-bought second hand in 2002 with ODO reading at 30700Kms-has now run 165000kms.Only I have driven it from 2002.Now some oil spill is seen on the engine cover and the exhaust smoke, a bit white.And the engine gets overheated in hot conditions and uphill journeys ,the power ,a bit less than before.I have to fill a addl. litre of 20w40 engine oil betwee oil refills(5 ltrs)which I do @ exact 5000kms.I want to know about the life of the engine as also whether it can be rebuilt perfectly? If so where(Kud u suggest a good engine rebuilder-TVS & Kuttukkaran in Kerala does not happen to have a good track record-just OK)? Some discourages engine rebuild citing reason as"XDP3 Peugeot engines can never be perfectly rebuilt".Is it true? If so, can I put a new DI Bolero engine there ?(Does law allow that) I love the vehicle since it has never let me down and has been my faithful partner in all ups & downs...