Western Europe can buy their gas or oil from anywhere in the world. Contracts don't mean anything. If they pony up a few extra % points, they can buy what they want. Do you really think oil-producing countries that routinely nationalize oil and gas fields will balk at tearing up existing supply contracts to divert fuel to Europe for a few dollars more per barrel or mcf?
The reason Russia's stock market tanked 12% is because domestic investors understand that the EU, with its $32K average per capita income, is relatively insensitive to fuel price increases whereas Russia ($13K per capita GDP), whose economy is roughly 50% or more oil and gas dependent will have issues dealing with fuel price decreases resulting from a Europe- or worldwide trade embargo. Russia will have to sell its oil and gas at cut rate prices to China and India, which were said to be offering a steep discount to the market price for Iranian oil, while sanctions were ongoing.
You’re way off.
Changing from Russian gas would require HUGE infrastructure costs.