Hi,
Here is a link to the [https://download.lenovo.com/consumer/mobiles_pub/lenovo_yoga_2_13_hmm.pdf|service manual] for your laptop.
Scroll to p.43 to view the necessary pre-requisite steps and then the procedure on how to remove the systemboard.
Scroll to p.62 for the part numbers for the various systemboards available for this model. Search online using the appropriate part number ''only'' to find suppliers of the part.
Hopefully this is of some help