1998 Chevy Cavalier check engine light

ok i have a cavalier and not a lot of money my check engine light went on i had to buy a battery and a new alternator then it was fine month later went on a trip about 30 to 45 miles there and back my transimisson hose had a giant leak had to replace that worked fine for about a week then took a short drive to the store today and there was like a wistling sound or a whine got in turned car back on there is the check engine light again every time i take it to a place i end up spending bunch of money my dad said it use to go on and they would find nothing is that the thing again or should i take it back to a shop