Just in case--Exhaust systems 101

I finally talked to the mechanic who's going to install my new cat/02 sensor right after Mem. Day. He's never seen my car but warned me that other parts of the exhaust might need replacing when he gets under the car & starts trying to remove the old cat. Sounds perfectly reasonable for an 8 year old car, & I'd like to be prepared. (Please God let it not be the manifold or whatever that really expensive thing is called.) I guess the most obvious problem might be getting the rear 02 sensor off in one piece, right? So I guess I should be prepared to buy a new one. Next most likely is a rusted-out muffler; they don't last long in Maine.

I've searched the forum for muffler info & found lots of it but don't understand most of it (too many acronyms). I don't care how a muffler SOUNDS--my next door neighbor is a pain & I don't mind waking her up prematurely; I just want the most economical one that works well & is most rust-resistant. And a readily-available one; I won't have time to order one on the net.

Are there any absolute no-nos in mufflers? Any that stand out for value & longevity? Is stainless the best buy in the long run?

Is there anything else I should specifically ask the mechanic to check out while he's under there?

Is there an AutoZone near you? They sell an OEM-replacement (which means it's the same size and supposedly the same quality, not the same brand) for $17.99 with a lifetime warranty. Naturally, it won't last a lifetime, but it should last 3 to 5 years, and then you get a new one for free (of course, you have to pay the labor to install it).

They also have a "turbo" muffler for $16.99 -- but the turbo has no warranty. I'll pay the extra buck to get a lifetime warranty.

My local AutoZone has the XJ muffler in stock at all times (except when I buy two on the same day).

No, no Autozones do I see in my phone book; I'll check tomorrow to see if there's one in Portland or Lewiston/Auburn. That price sure makes me happy. I'll check w/my good independent parts store & see if he has anything comparable in price & warranty.