Am i being taken advantage of.truck stopped running 04 f350 diesel.180,000 miles

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Oil pump changed cost 2186.00, chngd alternator 428.00, said need to chng fuel injectors 3000. No lights or sounds made it just stopped running and would not start again. Scared I purchased the wrong work truck. Also wrong mechanic should I keep going or trade it for Cummins/chev 6.7 or will this be the end of expensive maintenance. HELP What seems to make the problem better or worse? Nothing running great no noise How long have you had this problem? How can I tell if what he replaced was right and not just a oil light