If you use my approach all you’ll need to do is update the data each time one of your blocks changes (you can store this as separate data in chunks) and add a blend function right before the GLStateManager translate call. You could also adapt the code to use a TESR (not a FastTESR, because you need GL access) if you wanted
Since minecraft modding is complicated there really isn't a documentation. Learn by reading through the code others have made and understanding it. Look at vanilla's code first, then start looking at open-source mods on github. There are example mods too, like Cadiboo's example mod.
For the love of everything that is holy don't ever think about watching those terrible youtube tutorials though.