If you are in Islamabad, you can go to the below mentioned workshop near Golra Islamabad. They are really expert of Suzuki plus very trustworthy gentle people. They won't charge you much & will never try to rip you or miss guide you to make money. You can give him my reference (Asad, the blue Liana-06 owner)
Javaid : 03335609584
Shahid : 03336866125
Yes CNG Kit service + General tunning + Oils(engine, brake, clutch, steering) etc checking would be required.
One last thing.... Plss plsss plsss don't get your Liana ruined by some roadside mechanic for saving only 400-500 rupees once. They can't even tune it properly. They will charge you 300 for tuning & Suzuki dealership will charge you 500... So difference of Rs 200 is nothing when you see the negative aspects.