Experience of buying was good but the guy who i bo...

Experience of buying was good but the guy who i bought my car from told me all maintainance was done but after barely a month the engine light came on and turns out the transmission oil was terrible. It was black and smelled. After being assured that all maintainance was good, now i find out such a big thing was not done. Being a nissan, transmission oil change is very expensive! Advice: Always check oils and stuff before buying and do not rely that they will do it for you. It was a 2015 car that I bought.