Alhamdu-lillah, today I successfully completed the swap (Well, needs some time to evaluate how successful it is!!!)
Against all my love for QG18, i respected the opinion of 95% of people recommending to go for QG15.
The vehicle has become a rocket, reached from Saddar to Isb in unbelievably quick time.
Damn, it requires a bit of responsibility from a road rasher like me, overtaking 12-15 cars from left.
The engine started in quarter sulf right after installation. Everyone was saying that you got extremely good engine, MashaAllah.
Summary of Cost:
Engine with complete installation after adjusting E13 = Rs. 43,000
Oils (Engine Oil - Needs to change again in 1-2 days, Gear oil, power oil) = Rs. 2,500
Left goda = Rs. 1,000
Mithai 
= Rs. 500
Upcoming Approx Costs:
Engine Oil and oil filter = Rs. 2,500
CNG kit installation (They said get it installed seperately for EFI engine) = Rs. 2,000
Speedometer cable (Wasn't working at the time of swap) = ???
Fuel guage (One stupid electrician charged Rs. 1000 last time, with no result) = Rs. 1,000 approx.
So overall cost of complete swap comes out to be around 53-55K
