Replace crank shaft sensor?

I'm having a series of issues with repairs done by my local dealership. I'm having to do a lot of work on the car, and I don't know if it's due to the age of the car, or an issue caused by previous repairs.

I brought in my car for routine maintenance on 10/4. I was told I needed a new head gasket and struts. The repairs were expensive (cost $5,000.00, car blue book value is $3,000.00), but I figured the car would be in even better shape afterward.

A week ago, all sorts of alerts started coming on; tire pressure gauge (I checked, my tires were fine), check hybrid system message. I took it back to the dealership on Friday, where they kept it until Saturday, said the error messages were old messages, gave me back my car and said all was good.

Yesterday (Sunday), the Power Steering alert came on in the car, causing it to shift into neutral and lock the wheel. I had the car towed back to the service department. Today after inspecting it again, they are saying that the battery was drained and I need a new crank shaft sensor.

Can these things be related? Could the error codes be a symptom of a larger problem that the service department is missing, or possibly caused by the head gasket and struts repair?