Needs guidance in setting direction!!!

I am basically a Mainframe Developer/Analyst and have IBM DB2 DBA Certification. I have decided to shift into SAP XI area and preparing for Certification.

I would like to focus on some other related areas apart from XI. My idea is to learn ABAP (I heard it's similar to COBOL and won't take much time), MDM.

Please suggest me based on your experiences, what areas I can focus based on my previous experience. Also suggest where can I find related information.

Thank you very much in advance for all info and I assure will be generous in awarding points.