Employment Law Questions? Ask an Employment Lawyer.
I'm sorry to hear this.
1. They can force you to take a temporary assignment.
2. They are not necessarily required to pay for travel or mileage but you should certainly ask since you are trying to accommodate them.
3. They can fire you with or without cause under California's at will employment laws. Refusal to obey a directive from management might also prevent you from seeking unemployment as well.
I'm not trying to be the bearer of bad news, but it is important you get truthful and accurate answers to your question.