I was wondering how much of a job it is to replace a catlytic converter on my '97 Explorer 4.0L SOHC? Someone recently mentioned to me that it's an $800 job replacing the whole system because it's a Y-shape and you can't just replace the catalytic converter alone. I haven't gone under there to see set-up. Is this true? The car has almost 160K miles on it with a number of other things that need repair. Is it even worth fixing? It's probably only worth about $1,500. What harm would I cause driving around like this?