weird noise and leak

I recently went and had my coolant flushed and had the serpentine belt replaced and immediately after the SES light came on..I returned to where they fixed it and the code showed a malfunction upon starting and the light went out..1 week later I started hearing a squeaky noise from the engine and 2 weeks later add a small leak to that and now the SES light has returned. I am going to return and get the code again but would appreciate any suggestions since I know nothing about cars. :banghead: