Hi sir,I can help you here,but a 9 year old car ran only 40k kms is low and over that some suspension work needed.Hmm... Sounds Fishy
1) No,You may have to change or Recondition the whole Suspension System but though Try changing the springs and please check if that works.
2) Same like first;Please check if this fixes the problem.
3) I don't know the approximate cost as it varies much for different cars.But Maximum is Rs.15k for cars like Santro.
4) Nope,it is not possible but you can get Suspension Upgrade kit but it is to handle more power from the Mods that could be done to the engine and it is costlier and Hyundai a.s.s won't even touch that if some problem.So I strongly advise you to take her to Hyundai a.s.s and check her.The will provide and Install 100 % Original parts.
Other points to check is is any Rust ,Dent,Corrosion anywhere over the Suspension parts as they cause big damage to your car.Another is your Tyres and Rims.Please check if they have Rust,Dent or are Wornnut as they can also be the culprit here.Thank you