I need some help…

I’m an aspiring professional writer and recently finished my first book. I have some questions on what to do next.

First of all, I would like to know if I should or shouldn’t use a literary agent. If I should, how much would it cost me and what do I need to do? What are the advantages of an agent? Is it worth going after that right in the beginning?

I wrote a fantasy genre book and if possible would like some recommendations for agents and/or publishers that like this kind of book.

Also, I would like to know what the processes of getting an agent are or, if I shouldn’t get an agent, what the processes to sending the book to a publisher are.

Thank you for your time.