Best ofl luck with the project @alinaqwi1.
If you have overhauled the engine awesum.
Now before overhauling the suspension you should do is buy a rubberized undercoat ICI, Berger etc take the car to the service station get it propy washed from underneath and spray the coat under the car. 3 coats are required and it is prepared using petrol. And your car is rust proof for quite sometime...
I am asking you to do this before suspension overhaul because any rubber part will get damaged by the coating.
For Noise reduction and for you AC to work in summer. You need to soundproof/heat sheild your car. You can buy sound deadening for the doors and boot online. And use Master Industries Jumbolon for the roof and the floor. The sound will be reduced so as the heat in the cabin making you AC work..
Get the suspension overhauled for better ride. That's the best you can do with out modifying anything.
And in the last go for your cosmetic changes. I will say keep it as much original as you can
For ideas and suggestions check @nnabeel Bhai thread 'My Mehran MODS"