While you can upgrade the RAM [guide|103417]
The CPU may not be replaceable as the low end models have a soldered CPU, the higher end models do have a socketed CPU
Here’s the low end models logic board
[image|2042803]
There is also no graphics card, its a chip soldered to the logic board. Your only option here is to replace the logic board with a better Radeon Pro 555/560 GPU GPU chip.