Hi,
Here is a link to the service manual for a Lenovo S8-50. It shows that the touchpad and LCD (Item #4) is one unit.
http://www.manualslib.com/manual/821677/Lenovo-Tab-S8-50.html?page=41#manual
This link shows the part number for the LCD/TP
http://www.manualslib.com/manual/821677/Lenovo-Tab-S8-50.html?page=42#manual
Here is the start of the manual. reading through this shows how to dis-assemble the tablet to gain access to the LCD/TP unit.
http://www.manualslib.com/manual/821677/Lenovo-Tab-S8-50.html#manual
Here is just one source for a replacement LCD/TP unit. Just 'Google' the part number (5D69A6N2YU) if you want more options http://www.ebay.com.au/itm/5D69A6N2YU-Lenovo-TAB-S8-50-LCM-Screen-Assembly-/181854750943
Hopefully this is of some help.