The hardest stuff to master are the events and area based elements. I'd advice any rookie or anyone who wants to learn to just use some level as a base and move things arround then see what you can add and change... then you can go and have some real fun with it.
I personally have only done 2 entire stages, one that was simply a test and another one that is a remake of the first stage from SMB2.
The trailers for Newer SMBW looks amazing, Reggie is such an amazing app, I cannot believe hos easy it is to integrate those stages with Riivolution too!
everyone did an amazing job!
BTW the music is awesome and very true to the NSMB feel!
simply cannot wait!