Hi Megha,
Below are my understandings for your 3 questions.
1) Initially as you are switching from one domain to another you must be aware of the basic knowledge for that latest domain(Healthcare).
Any domain might have many applications based on that. The testing procedure will remain same , how much you have the domain knowledge better understanding you will able get of the application and able to test better manner.
2) Automation testing is only for increasing the efficiency and accuracy too. It reduces time time , man power in Long Run. For that you need to write the Script proper and that is a manual thing .You need to understand the application well and it should be well maintainable.
So Initially it might eat up ample amount of time. but once it is done , you will found it beneficial.
3) For interview questions go through Blogs , forums.
Regards,
Nilanajan