i am the one of the owners of chevy joy 1000cc CNG FF.
regarding your questions let me try to answer them:
mechanic:
chevy Es/Joy does have Multiple fuel injection system as it is better than EFI. any mechanic which understands the working of honda city/civic or santro can perform all the technical moderations and working on its engine. the engine bay is just like honda civic 1.8. compact sized.
Parts availability:
as far as parts are concerned, they are available in the market not so widely but alto, santro components could be fitted in the car. the spare parts arent any issue if you are buying a new one or old ES korean assembled. less maintance is required in this car (internationally recognized)
Price of parts:
some one mentioned that it is expensive, i think it isnt. if you compare price with mehran or alto it may be costly but with santro or coure it is more or less equal. besides 70 % components are still imported by nexus from korea where 30 % are purchased from pakistan as per govt regulations.
Resale:
i agree resale is less, but if comparing the merits and demerits it is negoitable.
utility:
the car is equiped with semi hard shock absorbers specially tested and made for the car, so often driving on bumpy roads, it gives a feel like you are driving in honda.
suspension is quite excellent and the car is stable whether you are driving in sunny day or in rainy and windy season.
its upon you whether you wish to have a old japanese vehicle or a new one.