Its not too hard to do actually .
The Chinese receivers are shaped a little different ..there is an angled surface about 61/4 in long on the bottom of the right side of your receiver.This shape has to be cut out of the new stock to get it to fit flush along that side and the heel of the receiver.
pic of the area with the angled surface
this pic shows the groove I cut into my stock with a dremel and a course file .
this pic shows how flush it has to sit on the stock at the heel and sides of the receiver .
As the final step you may have to remove a little material at a time from each side of the trigger pad area until the trigger group is correctly fitted and will pass the trigger test after assembly test
This test is VERY IMPORTANT.