Also, in the long run, you'd be better off using an HX711 module or an ADS1231 (or similar). You'll get a lot more precision that way.
InAmps are great for filtering out noise and giving you a nice, clean, amplified signal, but then you're still stuck with the common mode voltage range and the Arduino's 10 bit ADC so you can't get a lot of precision. When you use a simple InAmp you really want to use a high precision ADC with it... and then you're way over the cost of the HX711/ADS1231 options.