This was a clear, useful walkthrough — especially the point that the two protocols are about 80% the same, and that the choice is mostly about the people and the hardware, not just speed. Fixing area 0 and learning OSPF first also makes sense for anyone hiring or working in a company network, where someone else has to pick up the config later. The common mistakes section is the part I'd bookmark: splitting areas on day one is the same over-engineering trap I see in small-business systems generally.