When do you intend to travel? As in which month?
Which car do you have? model?
Take registration book, paid token tax receipt, valid driver's license, original CNIC. If the car is not in your name, then an authority letter from the owner along with their CNIC copy.
Check the tyres, service the radiator if it needs servicing, check break shoes, check brake oil, engine oil, power steering motor oil, gear oil etc.
Let's see, you have a total of 800km approx travel distance. If fog is not an issue, you can start your journey at 5AM in the morning from N55, connect M5 at Zahirpir interchange through Kot Mithan/Chachran Sharif in approx 3 hours. Travel all the way till Sukkur on M5, and then take N5 from there. With 2-3 journey breaks of 30-40 minutes each, I think you can easily reach Karachi toll plaza by 6PM within daylight hours. Add the time to your destination in Karachi, which can be anywhere from 20min to 1.5 hour from M9 toll plaza.