Since my mackbook pro has "El Capitan" steps below but it will be the same for SIerra and HSierra.
Restart the computer and after the chime press and hold down the Command and R keys until the Utility Menu appears.
Select Disk Utility from the Utility Menu then press the Continue button
After Disk Utility loads select the SSD (out-dented entry with the mfgr.'s ID and size) from the side list.
Click on the Erase tab in the Disk Utility toolbar. A panel should drop down.
In the drop down panel set the partition scheme to GUID. Set the Format type to Mac OS Extended (Journaled.)
Click on the Apply button and click on the Done button when it is activated.
Select the destination volume from the left side list.
Select Restore from the Edit menu of Disk Utility. A panel will drop down.
Select the source volume from the drop down menu in the panel.
Double-check you got it right, then click on the Restore button.
Destination means the SSD. Source means the internal startup drive.
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Now you can follow these instructions to open the laptop and replace the disk:
MacBook Pro 15" 一体化机 2010中期硬盘更换