For number plates, best to visit Excise office with the file and find out the status. If you have not followed up or received the plates, chances are they will accept application for the new Ajrak plates which you can get in whatever lead time they are following these days.
For maintenance, visit Jamil Autos which is on Sharae Quaideen near Quaid's mazar. You can call Irshad over there 0300-2237538 for time and location help. Recommended by many PW's here and I have got some work done myself from him, and overall satisfied. He can check the car overall (engine, mechanical, electrical, etc.) and suggest maintenance steps. Besides getting any issues fixed, you should change the fluids since you say no good maintenance done for a long period. For tires, many different markets but better go for either general tires from authorized dealers, or depending on your budget go for brands you can afford, but from authorized dealers and with recent manufacturing. A couple of stores in front of Liaquat National Hospital are good, but you can also check Khalid bin Waleed rd, and other markets depending on your location.