CEL, VSC TRAC, VSC off -- how to cure code P0420?

What is your question?

Would a bad catalytic converter cause the car to catch on fire? Lights came on Thursday, have driven 10 miles since then and today saw dark smoke coming from tailpipe during idle. Mechanic diagnosed Code P0420. Said ok to drive a bit but not a lot. Should I drive or have vehicle towed? Going back to mechanic tomorrow -- 10 mile drive.

How long has your 2002 Toyota 4Runner had this problem?

Started Thurs while I was driving, and today is Sunday. Have driven 20 miles since lights came on.