SAP NW 7.31 certification

Hello,

I am planning to do SAP Basis certification. I have 4 years of work experience (2 implementation proj and 1 upgrade proj).

I have two questions.

1)Whether I should go for associate certification or professional certification?

2)SAP certification study material.

I have found one basis certification that suits my profile (please let me know if this is correct)
SAP Certified Technology Associate - System Administration (Oracle DB) with SAP NetWeaver 7.31

Also I can see in course details that there are different sections like DB administration, System Administration etc and in those section reference links like TADM51 or ADM505,ADM506 etc are provided. My question is whether its necessary to attend classroom training? If not where I can get the pdf/authenticated course material (hard copy).

Regards,
Pratik