I have no idea about parcel shelf price but i heard somewhere that it is well over 3000/-RS.
When i got shocks for my Cultus some year's back they costed me i think about 8000/-RS from dealership.
If the shocks are orignal one's and they haven't been repaired earlier then i would suggest to get them repaired from some banday ka puttar. If repaired correctly they will serve you another 4-5 year's atleast.
It depends on which kind of road's you drive and how you load the car. For me it's the front shocks that need to be changed earlier.
If you are able to get your hand's on a good gearbox then buy it and swap it. Pour in SGO SAE-90 gear oil instead of others that oil is thick enough and also recommend in owner's manual. I hope so that will keep the gear noises in control.
BTW before changing gearbox get another axle rod used one i think new rod's only aren't available. That unbalanced rod can also have a negative impact on gearbox.