94 Chevy blazer s10 lt transmission issues
 

I was given a 94 Chevy s10 blazer. My son was driving it and said the speedometer would not go over 60 mph but that the truck was. Then that night coming home from a school event the transmission didn't want to shift. It is an automatic. Upon checking the transmission fluid he said it was black like it had been burnt. I have think the vss went out but he thinks it's the transmission. Is there anyway to know before I spend the money to have it repaired? If it's the transmission the truck will go live at the nearest junk yard. I just can't afford a new transmission.