I think you should go for overhaul. Your mechanic is demanding too high. You just need to change the rigns and valve seals and may be some valves if damaged but not more than that.
The labour for this kind of work is about 3.5-5k and else would be the cost of parts and khiradiya's work.
My 4efe engine was started consuming oil and also gave smoke. I just replaced the rings along with valve seals and timing belt and some other small parts that cost me around 4-5k rps from Gawalmandi Rawalpindi. The complete work cost me around 13-15k including oil and filter etc. It is about 1 year now and my car is running perfectly.
In Karachi I think the prices of the parts are less than in Rawalpindi.
So you should get quote from other mechanics and also khiradiyas for head works and go for overhaul.