Go with aamco over stealer. Aamco uses Alldata for labor quotes (hours).
3 - 4 hours sounds inadequate, I think more along the lines of 7 or 8 is in line. Not sure about the 9, but on a lot of vehicles you have to remove the engine cradle/subframe, support the engine from above/below, and then remove the tranny. All that in 3 or 4 hours is wishful thinking.
I have seen a couple folks on here who had torque converters replaced under the 60k warranty, but had a problem all along, and never just "creeped up."
If I were you, I'd look at buying a good trans from a salvage yard, and purchase an extended warranty from said yard on the trans. They will freight it to the shop of your choice.
You can try calling LKQ Corp at 800-385-2727, then go ext. 5344 and ask for Matt. He is one of their more intelligent reps who knows quite a lot. He will give you pricing, location, warranty info, mileage, condition, etc.
You can also try car-part.com and search for transmissions for the CX-9.
Buying a used trans has some serious benefits: mainly when you buy a used trans, it is just a matter of drain, drop, replace, refill and off you go. Places like Aamco have the ability to overhaul a transmission and replace internal parts (which dealers refuse to do) but replacing internal parts usually involves labor to dis-assemble the entire transmission, replace all the seals and gaskets and put the whole thing back together.
If my trans every went out or any part of it, I would try my hardest to find a low mileage assembly, buy an extended warranty from the yard it comes from, and have a reputable transmission shop install it. That is your best bet.
When it comes to out of pocket work, you may want to leave any dealer out of the picture.
Long story short- I've been feeling a shaking/stuttering coming from my 2008 mazda CX-9 GT (AWD) at 30-50mph in 4th or 5th gear (only when keeping constant speed- accelerating it goes away). So I took it to the dealer (and I'm out of warranty and at nearly 110K miles), and they're telling me that the Torque converter needs to be replaced, so therefore the whole transmission needs replacing. At a cost of $3500+
AAmco says that they'll look at it for free and replace it for $2000-2500 but cant verify it without looking at it.
Does this sound right? has anyone had to replace their Transmission yet?
Thanks!