The replacement battery was ~$7 USD including shipping, while the replacement screen (all-in-one digitizer/glass/screen assembly) was ~$15.50 USD including shipping.
The special screwdrivers/suction cups/spudgers/etc required to perform the procedure were included with the parts.
The swap process was relatively straightforward & lots of high quality photos/videos detail the entire procedure. Numerous guides are freely posted all over the internet.
Getting parts for a cheap Android device, however, proved more expensive than the cost of replacing the device (ignoring labor costs). The market is so fragmented it seems harder for an efficient parts supply chain to develop organically, let alone the knowledge/repair guides to effectively use those parts.