Bro, we all are here to help each other by our experiences and discuss different issues, like there is very informative discussion is going on between @imrananr and @faisal.imtiaz.16. Go back some pages and you ll find information on CVT oil changing. Read all carefully and you won't be a newbie over time.
For changing and purchasing oil, i prefer Makki Oil store located near Wapda Town or Filter House, they have different branches which are located in DHA, Infront of Qazafi Stadium and Montegomery Road, select any of it which suits you.
For maintenance like Throttle service, Fuel Injectors cleaning, ECU scanning etc, Magic Motors is a good option and they are economical too. They are located in Model Town. If you want to spend extra, Toyota Airport Motors is a good option.
If you have any other queries, please feel free to ask.