I would only recommend upgrading the bike if the frame is straight and in excellent condition, it's one of the higher end models, and it fits him well. Even then, the idea of you helping him, with not knowing that you can't just add the shifters and cables, indicates that it's not a good idea. I'm betting that the examples in the link were of people who for the most part had a lot more experience and knowledge under their belts. What you are contemplating is not only expensive, it's a fairly complex and very time consuming exercise when starting from a point of relatively little knowledge.