If you are good with hands and tools and have some sense, and are willing to read and listen closely, and not go too radical, then you have a decent likelihood of success on your own. My first performance engine was one I built and I had not done a complete motor before; I read and read and read.... and read some more. And asked questions at the local shops. But the dilemma is understood. The advice is because the crate engine route is a bit of a crapshoot; you may very well end up with a decent piece, or not.