There is not an easy answer to this question, it depends on your cabinet layout. it is something that I have done in less than a day before with about $50 in material so the total charge was $450. plus the cost of the new appliances.
But I have also done it in a kitchen that it cost the homeowner about $2,500 plus appliances due to the fact that we had to remake a cabinet to match and rewire the oven from the circ. box on the other side of the house. be aware that most double ovens reqire a larger circuit and thicker wire.