2000 ford winstar engine light came on again, already had mass air flow sensor and couple other sensors replaced. The other day the engine light started flashing and i guess the van was miss firing. Auto shop at first thought tune up and oil change since gas got into the oil from miss firing. Then they said that was not it I needed a new engine, then today they said the right bank (or something) and three intake valves needs replaced. Will this fix my problem?

 

It is not my intent to dispute your shop's diagnosis.
My suggestion would be to get a second opinion.
A good shop usually will not mind your getting another opinion.
The answer to your question should be supplied by the repairing shop.
There could be several reasons for the misfiring and personally I would prefer a more definitive answer as to what caused the problem.
Did the same shop replace all the other parts previously?
If so , I would think they should have done a more thorough diagnosis before replacing all those parts.