Hi Harin, here goes...
1.differance between escudo and grand vitara.
Its the same thing no difference, Grand Vitara is the export version and the Escoudo or the Grand Escoudo is the Japan Domestic model ( JDM ) . There are some differences between the two such as heated seats, leather seats, sun roofs, different lights, etc.. so you need to look out
2. any known issues. Assuming you are refering to the XL 7 version, nothing major and the V6 engine is solid, and heats up like hell, so proper care should be taken wrt the cooling system and the oil changes etc.. Some are know to have all sorts of electrical issues, but guess that is common with almost all cars these days. In my view nothing major to be concerned of.
3. agents attitude
Err.... this is a tough one, A*W they are good people, but the problem is the place is full of Marutis and the smaller cars, so they are not very focused on the XL-7, some of the mechanic have no clue and simply useless. But the customer care part is done well. I wish they had a seperate unit to handle the 4WD vehicles only.
4. repairability, maintainability , reliability
Anything can be repaired, maintenance is not very expense ( relative ) in comparison , also prices of parts are probably same as for any Toyota, but difficult to find. However the agents will bring down any part within a few weeks so no big issue and nothing to loose sleep over.
5.comparision or parts cost - Said above
6. average fuel ecconomy, - 5 to 6 Km/lt Max, but if you could find a manual this will be much better.
7, resale value - Very low, but since you are anyway buying from the second hand makets ( which has already taken the drop ) it cannot do down any further. Maybe another 100k max, since you are adding another user.
8. reasonable price for 7 seater model. Anything between Rs 3 to 3.5 Mil . Sometimes its worth to pay more for a one which is well looked after after. This is a big vehicle, and you get almost all the benifits of a good off road vehicle, so its good value for money.
8. parts availability Already said