How much is cost for checking baggage (50kg) on high speed train on same train you are on?

I would like to take some household effects when I move from Chengdu to Beijing. I need to know how much it's going to cost to take my stuff on the same train I travel on.
Also, will there be porters (for a price, of course) who will help move the stuff from the cargo train to a taxi or other vehicle?