I managed to replace a swollen battery ($33.25 on amazon) that popped the screen, but this is not for the faint of heart. Special emphasis needs to be placed on not twisting the digitizer connectors as they are quite fragile ($119.99 on ebay for a new digitizer). It's also easy to damage the force-touch sensor ($24.95 on iFixit). You also need adhesive gaskets ($12.98 for 5 on Amazon)
iFixit lists all the parts required but were out of stock on all but one of the items I needed at the time.
Battery:
https://www.amazon.com/gp/product/B01MV2...
Digitizer:
http://www.ebay.com/itm/262744629522?_tr...
Force Touch Sensor Gasket:
[关联产品丢失或禁用： IF308-013-2]
Adhesive Strips:
https://www.amazon.com/gp/product/B01N4J...