1992 Plymouth Voyager tapping noise

1992 Plymouth voyager mileage: 110K. Help. After replacing our van's timing chain and radiator, our mechanic said the tapping noise I am hearing is coming from the valves and I need a valve job (approx. $1200). I wanted to make it one more year with this vehicle. Here's my questions” What will happen if I do nothing and ignore the tapping and drive it till summer when I can look for a new vehicle? Will the engine fail or lock up? Would it be okay to take it on a couple 300-mile trips? Any advice on how to decide when to call it quits and go ahead and buy another vehicle? Thanks--lots of good info here.