No problems just a challenge!
I just wanted to make an iPhone 3GS myself. So I ordered the individual parts (back cover, dock connector, logic board, camera, display assembly) and put the thing together.
Perfect with repair instructions from ifixit.
Go to ifixit if you have problems with iPhones or Macs. The repair guides and instructional videos are really good. Follow them step-by-step. It always works.
Thank you ifixit!