need some advice please...

I am just completing my final year at university doing an EC, IS degree. I have decided to continue in the Database field and i have purchased "OCP: Oracle8i DBA Certification Kit". I have only basically touched on Oracle at univerisity with basic design and SQL coding and was wondering if certification was the best way to go.

What is the difference with Oracle 8i, 9i?

How long on average would it take to complete the exams for OCP DBA given self learning...and how hard is it with no guide?

How much money are some people with certification on in here....if that is not too personal?

How important is knowledge of Linux, Unix?

any answers you can provide me will be greatly appreciated and any other guidance you can give will be warmly welcomed.

Thanks.