Hi Ashish,
Welcome to TAI, this is a forum where you get plenty of support from friendly seniors. My restoration was greatly supported by TAI members. I recommend you to post pictures (inside, outside, engine bay, specific rust issues etc. This way we can help you by suggesting easy fixes/solutions.
Few suggestions from my side:
1. M800 is easy to restore than any other car
2. Not everything needs to be restored, many parts such as radiator, blower (fan), seats etc can be repaired, thus saving a lot of money.
3. Function over form, focus more on the engine, suspension, brakes initially then take care of seat covers etc.
4. Feel free to ask anything about your car here.
5. I will PM you my number, lets meet up & I am curious to see your car.
Solutions to your existing problems:
1. Engine overheating -
Flush radiator, fill new coolant (coolant + water). When I say flush, it is not just draining, remove the radiator & have it pressure washed at any service station.
2.
Change Radiator hose kit - costs only - Rs.160/- so no coolant leaks in the near future.
3. There are only 3belts in Maruti 800, replace all of them
>
Dynamo belt - approx Rs.90/- (bosch make)
>
AC Compressor belt - approx Rs.60/- (Bosch make)
>
Timing Belt - (not visible from outside, it is inside the black casing) - MGP - Rs.700/-, local Rs.200/- max
4. Brakes - if there is any sign or damage/rust on the brake booster (if equipped) or if there is no brake booster, then buy new Brake booster kit
> KBX Brake Booster (with master cylinder, pipes etc) - Rs.3400/- approx
> New Brake Oil - Castrol/any brand - DOT4 - Rs.250/- max
> KBX/Bosch/Delphi - Disc Brake Pads - Rs.250/- (+/- Rs.15/-)
> Inspect all break lines, if found any leak/weak sections of the pipe get it replaced
5. Gear Rod Play - Replace gear rod bush kit (plastic parts below lever), if the round ball part of the lever is worn out, then replace the lever itself. Varun recently replaced it check with him for the price.
6. Accelerator, Speedometer & Clutch cable - DO NOT BUY REMSONS BRAND! MGP parts will cost you around 300max for all 3 together.
7. Throttle body - I have no idea about this, I am a carb guy, mpfi gurus can help you here.
CAUTION: DO NOT TAMPER any wiring, in carb cars it is easy to fix wiring issues, but in MPFi there are too many wires, so please be carefull.
Other things to change,
1. Wiper blades
2. Cleaning wiper water tank & coolant reservoir tank
3. Fuel filter & air filter
4. Oil opt for simple mineral oil - 3ltrs approx cost - Rs.800/- 15W20 Castrol/Shell
Use this oil for may be 500 kilometers & drain it off. Again fill it freshly with new engine oil. While flushing use flushing agent.
5. Gear oil replace straight away - No second thoughts here.
For pictures & prices of most of the M800 parts, check my thread -
http://www.theautomotiveindia.com/forums/ownership-reviews/6379-bought-my-first-car-maruti-800-ac.html