Alhamdullilah my car is in great shape. Partly because of the fact that it has been only in my use since it was bought brand new and also because i take alot of care of it. Wash it myself in and out 2 times a week, get the oil/air filters and motor oil changed every 3000kms, get it tuned, aligned and balanced every 6 months and also run it as neatly as possible. I believe that one should enjoy the drive of the car rather than use it to race to another place
Also, when you know your dad works his ass out to provide you with necessities of life, one should respect and regard the hard earned Halal income 
As far as cost is concerned, like i said, its a estimate, a wild estimate to be precise. It may be less than that, i am not sure, you need to visit a mechanic for the final verdict. You may change the Kia but as far as i know, i am so much used to my car and know it in and out that i feel comfortable with it and if there is an issue i get it resolved. So you might want to try the overhaul you existing car. But thats just me, you should go ahead with watever you feel comfortable with 
Best of Luck 