Bhai, your unit has option for GPS, so you can use it. You need maps of Pakistan on an SD card alongwith GPS sensor.
The GPS sensor goes inside the top of the speedometer but remains inside the dashboard, so it is not visible. It looks like this
Source: Amazon.com: GlobalSat BU-353 Waterproof USB GPS Receiver: Electronics
The Garmin Sensor costs about 600 dollars and not worth spending money on ... you will still need the maps for Pakistan.
If I am not wrong, the maps are available from naqsha.net and cost Rs. 11000 on a 2 GB SD card.
I bought my headunit for Rs. 42000 and it came complete with the GPS sensor and the maps for Pakistan. The maps have complete coverage for 22 major cities of Pakistan, plus all the highways