RE: reset check engine light
Just resetting it will not fix your problem.
The check engine light has nothing to do with fluids. It is designed to come on when there is a problem that is effecting the emissions of the vehicle. It can be caused by many things. Some places will read codes for free, but that does not mean to just replace that part. For example, if its an O2 sensor code, that can be caused by an intake or exhaust leak. So if you guess and just replace the O2 but you have an intake leak, the code could come back.
If it flashes, it is likely catalytic converter damaging (possible misfire) but don't quote me on that.