Car would stop running while driving it and wouldn't start after that; changed the alternator and now it will start but it doesn't stay running. It stalls every time I try to put it in gear to drive it.
Is the check engine light on? A relatively common failure is the crank shaft position sensor which can cause the car to die while driving. As well as hard starting/No start. IIRC the alternator on a Hyundai 4 cylinder is typically on the exhaust side of the engine near the radiator. So it may be safe to assume that the vacuum hoses are untouched.