I am a lifelong DIYer and am always biting off more than I can chew. When my 4l60E turned out bad the first thing I wanted to do was rebuild it myself. After doing exactly what you did - checking the internet and reading attempts by others - I chickened out. I cannot believe how mature I must be getting.
I found a guy on clist that rebuilt mine for $550 and so far after 500 miles I am happy.
I agree with what has been posted - there are soooooo many little tiny details that can go wrong. Made me skeeert.