Hmm well Ameen Dear I have had Daewoo for the past 1 and half years. And am in Multan, meaning no Spares and moron mechanics here. Anyways you are in Karachi so you should have no problem regarding spares etc.
I think its a Great car.
The things you should look are:
1 - Look if the car is main Accident, dont if it is.
2 - Check Engine condition.
3 - Check A/C.
4 - When A/C on run the car for few KMs and see if it gets heated up. Faulty Radiator, Fan or Generator etc.
5 - Check starting, with and without CNG. Check Ignition Sulf.
6 - Eclectric system is a bitch if messed up, get it checked from a good electrician then decide.
As for the Officer scheme I guess the Car"s Registration No, and the papers. There are cutom clearance papers, that I got, see who bought it in the first place. But I think that the Taxi Cars had no like LPT or something like that. Someone else might give you more info.
Anyways Its a good car, if you are in Karachi or Islamabad.
Get it.