Unless i missed it, what year and trim is your vehicle. At midas, OBD 1 cats i believe, now dont quote me on this, are more expensive than obd II. You can do an intrusive test to check flow before and after the cat or get readings off the oxygen sensors, if they are marrying eachother or in other words, giving you the same reading, the cat is bad. but without more details it is pretty tough to help you out. If all he said was you need a new cat, he didnt give you what you needed to know.