I recall reading somewhere that you cant send products back to china because of their strange customs allowances and not allowing electronic equipment to be imported?
Yes. haha
Sorry. Take the box apart and send the part wrapped up in bubble wrap and in a box. It has to be marked that it is mainboard for repair. If you take it to the post office, it cost just under £6.00 and takes about 3 weeks.
To get it back is another story.
Some suppliers will just post it back to you, and some want to charge you ££££ for DHL