Chunck will know better, but I am going to say yes, it’s ok to mirror. As long as there is symmetry, if both sides look alike, I say mirror away. Also remember if you are totally totally new, it’s best to start with The Blender Basics Course:
https://cgcookie.com/courses/blender-basics-an-introduction-to-blender-4-x
Then ideally Modeling Fundamentals:
https://cgcookie.com/courses/core-fundamentals-mesh-modeling
That way you have the bedrock knowledge and then you can branch off to all the cool beginner courses.
