l have heard that driving on hilly region it is problem, cost wise how it is feasible, maintainance wise, it is said that more maintainance work come if you do LPG,

converting old car into lpg isnt supported as it is risky
its mentenence cost is little higher but it has a bit cheap running cost
its preferable to convert it into CNG insted
or if LPG only govt. certified

beware you have mentioned about the hilly region, do not change the car to LPG or CNG. let it run on petrol, because if u change from petrol to LPG or CNG the pick up will come down, and also LPG and CNG are not adviced in high altitudes and is risky also

You can use lpg as it costs you approximately one rupee per kilometre and the cost of petrol is increasing gradually.

In hilly regions LPG is not advisable especially for a zen carrying 5 people. There will be a drop in power & please consider the avilability & no. of filling stations for LPG at your location. If do go for it, then get a govt. certified kit only.
Abhishek