2011 dodge nitro help in Elberta, Baldwin County, Alabama

I have my dodge nitro at a mechanic right now and I have had it since February, he is telling me I have a seized engine and appears that nothing is wrong with but wants to charge me $4,500 for parts and labor. I am a single mom who is trying to get help looking at it to make sure that this is actually what the problem is. I can not afford to pay this amount and now I’m missing hours at work from having to get rides everyday, can someone please help look at it. It showed no signs of issues and just stalled at the store and then would click, it tried to start but stalled, the starter was replaced and same click.