2008 Toyota Yaris Engine warning light

In May the gas tank was filled by accident with the Diesel Fuel. The tank was half full at the time.
The whole system has been flushed at the Dealer.
The car was performing OK, however yesterday the "Engine warning Light" came on.
After inspection, the dealer suggests replacing:
catalytic converter
02 sensor
4 fuel injectors
spark plugs.
they also suggest that there might be further damage to the engine, not known at this time.
Is all that really necessary? Or is the dealer taking advantage of me?
What would you suggest as best option?
This is terribly expensive, and I can't afford it at all.