Wa'alaikum Assalam!
First off, extremely sorry that your post didn't get any replies and you had to struggle all on your own.
Were you able to find a reliable workshop/mechanic for the job and more importantly did you find a reliable place to buy genuine Toyota parts in Karachi?
I know it has been ages since you posted this here but since I am facing the same issue and I also need genuine OEM Toyota parts for my corolla so I really want to know. Your advice based on your experience could really help me out.
Thank you in advance buddy!