I am thinking about buying a used 2000 audi s4 that has some issues with it.

What is your question?

The issues with the car are 1)The car has an overheating problem that could either be the thermostat or the headgasket(if it's the thermostat I believe I can fix the problem myself)if it's the headgasket would an engine additive fix the problem instead of me paying big$$ for a headgasket repair? 2)The torque converter clutch is stuck open & is there a lubricant that can fix this issue? 3) abs is not working but I believe you can still drive/use the breaks with this issue? Any help would be greatly appreciated thankyou!!!