Chosen Solution

I would like to buy a body shell with a screen and buy parts and then assemble into a working computer? I have no experience doing this. Can anyone tell me anything about it?

Really bad idea. As a professional, I have stacks of old broken machines. I use them for specific parts. Just one failed part and computer will not work properly. Buying the parts will cost twice, on a Mac, as the whole thing. With no experience you are begging for failure. A better idea is to research machines with recalls from Apple that are still in effect by Apple. Then look on eBay or Craigslist, get it and take it to Apple for a free repair. Here’s a list of some but stay away from the 2011 machines as they are starting to balk on those due to age. https://www.apple.com/support/macbookpro