Assalaamu 'Alaikum Wa Rahmatullahi Wa Barakatuh Ghazir
Start with basics.
Do not even attempt to hate the car.
Check if the serial number from the engine that does match from the car or document.
Engines here can last at least 200,000kms unless the previous owner beat the heck of it.
Leave the paint alone (unless it's really bad). Just wash "service" and wax it. Just make sure it's not too rusty under it.
Disconnect the battery's negative terminal, and turn on the light switch for at least 1 minute.
Turn it off, and reconnect the terminal. This should solve the problem.
Make sure the battery and tire pressure are okay.
Change the spark plugs, air-filter, fuel-filter, oil (if necessary). Do the CNG tune-up (if equipped).
Try using a fuel system cleaner.
Clean the mass-air sensor locating between air-filter and throttle with contact cleaner only (Disconnect the battery first). NEVER use anything but that.
Not sure about the "boo" sound, it could be a clogged exhaust system.
If it revs high on first, or higher gears, change the transmission fluid and PRAY it solves the problem.
For safety purpose (if necessary)
Align and balance the wheels.
Check for the electrical system.
Replace the coolant with clean A/C "distilled" water. Keep changing it every 100kms till its clear.
Check for the CNG cylinder (if equipped).
Check for brakes and suspension.
If the car runs at least good. Just baby and take care of it for life.
These are the best possible answers I can give.