Does any one know what it would cost to replace a concrete lintel above my living room window?

we had a crack appear above our window a surveyor said for us to replaster and if it reappeared to replace the lintel there are a couple of hairline cracks in the concrete lintel the house was built 1960s so i was wondering what the cost might be in the region of and could the lintel all of a sudden collapse causing the window to break or am i just being a drama queen any advice would be greatfully received thankyou