One problem there - what if we simply aren’t able to find an alternative energy source thats powerful enough to replace oil? We use a vast amount of it. Hydrogen is a useful portable source, but we have to expend energy to in order to produce it. Its possible, regardless of the amount of money involved, that we won’t be able to solve this problem fully, and as a consequence the disruption will be huge.
Nuclear power is a possibility, but remember we’ll need to generate far more electricity than at present (what we use now + what we need to produce hydrogen to power vehicles). Nuclear fusion is another, but no-one knows if its really feasible.