SAP S&D and SAP CRM

[maneeshxnair]

I am doing my PG Diploma in CRM. I know the theories. I am very curious to do SAP CRM. However, I have been advised to do SAP S&D first before SAP CRM. I do not have a sales or marketing background at all. I would like to know if it is advisable that I do SAP S&D or SAP CRM. If yes, should I do S&D first or can I do SAP CRM directly? I am not sure and I need help very badly.