It is not possible to fix 7-inch infotainment system to 2016 model Tiago as the design is changed in the upgraded version. Moreover, we'd suggest you walk into the nearest authorized service centre as they will be the better person to assist you. You can click on the following link to see the details of the nearest service centre and selecting your city accordingly - Service centre
The exact information regarding the cost of the spare parts of the car can be only availed at the nearest authorized service center. We would suggest you visit the nearest authorized service center for further assistance.
In order to know the build quality of any vehicle, you can compare the kerb weight of the vehicle. The kerb weight of Tiago, Swift and Elite i20 are 950, 855 and 1066 Kg respectively. So in terms of built quality Hyundai Elite i20 will be the best option.