Travel by high speed train from Guangzhou to Zhongshan. Advice on ticket and luggage loading.

I am an oversea Chinese. I've planned to travel from Guangzhou to Zhongshan by high speed train. Please advise me on ticket purchase and how soon before departure I have to check-in my luggage. I have a suitcase and a cabin bag. I would like an escort if it is at all possible, as I am unfamiliar with Guangzhou train Station regarding safety and traveling procedures