Hi,
Here’s the [https://download.lenovo.com/consumer/mobiles_pub/yoga_710-14isk_14ikb_15isk_15ikb_hmm_201605.pdf|hardware maintenance manual] for the laptop. Go to p.45 to view the necessary pre-requisite steps and then on p.47 the procedure to remove the systemboard. Reverse the procedure and necessary pre-requisite steps to install the new board
On p.69 Item #4 you will find the systemboard part numbers for all the systemboards suitable for the model. (check against the Yoga 710-15ISK column as some are for a Yoga 710-14ISK only). If you search online using the part number only you’ll get results for suppliers.