If your main catalytic converter is dying, it will NOT trip a Check Engine light.
However, if your pre-cats (embedded in your exhaust manifolds) are dying, they can trip a Check Engine light. Pre-cats are expensive to replace if you have your stealership do it for you. If you're under 8YR/80K, the stealership is required (by law in the U.S.) to replace your pre-cats for FREE.
Did the stealership tell you what the exact code was? Try to find out the exact code, then do a SEARCH here on CEG for it -- you'll find plenty of good advice.
On 96+ V6 equipped Contiques, the vehicles are equipped with 4 oxygen sensors (O2). They cost around $40-60 apiece and really aren't hard to install yourself (most auto parts stores will loan you an O2 sensor wrench for free). Bank 2 is located closest to the radiator (e.g. easiest bank to access).
I've never heard of "Random Tech Cats." I'd be wary of any product with the word "Random" in the name!
