Faulty lambda sensor seems most probable to me, but that wouln't stop it starting. Could be an injector or the MAF, the coolant temperature sensor, or (I'm not sure about this; an exhaust leak?).
The EGR valve normally needs cleaning after 60,000.
Don't forget you may have multiple issues where one thing has led to another, or the non-start may be completely unrelated to the the stalling or the poor CO test.
I'd try and make friends with someone with diagnostic equipment, get one from a well-known internet auction site, or even take it to a garage, that's the first step, as otherwise you might end up replacing good parts and getting nowhere.
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