Most places that will supply and fit a battery will run a quick diagnostics check on the charging circuit, if you ask. Engine light may have been down to the terrible state of your battery, but as JazzyB said, worth getting it checked. But if it is going to cost big money (like a Honda dealer), I wouldn't bother. I had an engine management light one day and before I could do anything about it it went out and has never returned. Fault code, whatever it was, wasn't stored.