I studied this at length before I wimped out and bought a finished WFO. In my opinion, if you want to end up with a durable, quality oven with decent performance, you are in for a lot of work with a fair amount of logistical effort as well. I don't think most of the work will be all that difficult per se, but it will require a lot of planning, it will be very time consuming, and it will require effort to be precise.
If you decide to build yourself, I would not look for the easy way out. I think in the long run, you would regret it. The plans I've seen are not overly complex, rather they are designed to achieve many important functions. Shortcuts are going to, in many cases, compremise performance.
All that being said, buying a finished oven ended up being a lot more work and a lot more difficult than I had contemplated as well (and I'm not done yet)...