Would a faulty rear oxygen sensor be the cause of a jeep not starting? on 2000 Jeep Grand Cherokee

My daughters 2000 Jeep Grand Cherokee went through some major repairs this summer. The last thing the shop said she had to replace was the rear oxygen sensor. They said it would run for a while but should be replaced/fixed. Of course this wasn't done and now the jeep won't start and is sitting in the college parking lot. Could that be the problem and if so, estimated cost of repair?

Asked by for the 2000 Jeep Grand Cherokee
Don't think the 02 sensor is the problem. In fact no it is not!! Bunch of stuff it could be.
Not much can be done until it is tested by a mechanic to find out what it is. No need to list
a bunch of poss. componets that can cause this, as it would just be guessing and misleading!
Thanks for your quick response. After replacing most everything on the jeep we decided to throw the towel in and just get a new car. I could not face another repair that might still not make it correct.
Problem solved! Thanks for the reply.
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Highly unlikely...