So we bought a Quest SL from down south, everything looks great (I'm from a northern state) but recently we been having an issue where when I shift into reverse or drive from park or neutral it just dies. I hooked up a code reader and the one I'm using tells me it's O2 sensors, but when I took it to the dealership they said the CVT is shot and needed a new one, but they didn't exactly tell me what all codes were listed. A big question I have is, since the engine has 230k miles on it, is it worth buying a new/used one and swapping them out, or getting it rebuilt and if so are Nissan dealerships the only ones that can work on them?

Most cheap scanners only talk to the engine, so chances are you're simply not seeing whatever codes are in the TCM. Any shop can swap in a used one if you get the donor TCM along with the CVT. That will circumvent the need for programming, plus any codes in it will also tell you if the used unit has problems. I always suggest hooking up the donor TCM to your vehicle first for that reason. If it has a bunch of codes, you'll know there's a problem and you can take it all back to the JY and get a better one.

So that would of been my next question. Where would the best place to get one be. I have read in a few places that the cvt's only last around 200k or is that certain years

Depends on the maintenance they get, and the driver and driving conditions. The 6-cyls like yours will generally always make 100K even with no attention and harsh driving. We have a Murano in our shop that's pushing 500K on the original tranny with spotless maintenance and lots of highway. Most of them will fall out someplace in between.

Thanks you been a big help