How long do I have before extreme damage is caused by needing spark plugs

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My car wouldn't start so I jumped the battery had it checked and needed a new one. The day after it was replaced check engine light came on sometimes it would flash but mostly stayed on constantly. Occasionally idling high when stopped and sometimes not enough power when stepped on the gas. We have been having some extremely cold temperatures and I'm afraid all the fluids thick or frozen. What should I do?