quote from a service station to replace the crankshaft sensor?

I have had an issue with loss of power when accelerating and even my car dying. The OBD light is on. I just received a quote from a service station to replace the crankshaft sensor and get a tune up. They want to charge me 370.00 to do this. Is this repair easy to do on my own and is this amount a reasonable amount to pay for the problem I am having. They also suggest fuel injection and carb flush and air filter replacement.