You have two options for the DVD players in your car.
1st. Chineese made players having all the features including Fm, dvd, Bluetooth, sd card, usb, mem card, back camera option etc... Rockmars, dellson, tracking world, premier are some of the conpanies. It will coat you around 13000rs.
2nd. A branded dvd player like Pioneer, kenwood, sony etc. Without bluetooth the cheapest dvd player having fm, usb, aux, back camera option will coat you 21000rs. With bluetooth option will cist you 26000rs.
A single din pre without screen branded one starts from 6000rs.
I will recommend you to choose branded. If money is the problem then Rockmara or tracking world are good as they have warranty on them.
About the oils, use 5w30 or 10w30 grade engine oils only. Shell helix ultra, havoline formula, toyota petron plus and Toyota genuine tin pack oil(I'm using this) are good.
When you open the bonet, you can tell by the condition of the engine body and metal pipes if the car is driven a lot. 20k driven car is just like new. Look for any rusted bolts and nuts and check the tyres. CVT oil should be inspected after 40000kms. Go to any Toyota 3s shop and ask the mechanic to check the cvt oil. He will open a small screw below the oil chamber to see the oil. Color of the oil should be red and smell should not be like rotten eggs.
Auction sheet is the best way to check the mileage. Did you get it with your car? Get your car serviced and when it is on lifter, xheck the bottom. Check the headlights. Old cars has foggy or yellowish glass having scratches on it with a white scale...
Any more questions??