Start with the workbook. The material may be old but it's gold. Also, check out the resource page on this forum. I've posted a few items myself.
I've been a community organizer for a number of years also, and I have to say that in-person training is very useful. For me, the videos, workbooks and everything else online became that much more useful after training because I found outhow much my mindset is already fixed a certain way.
After the training, I pointed my colleagues to the videos and workbooks since there wasn't any training local to any of them. Each one of them fell in love with the concepts, especially talking about gifts, and "learning conversations" etc. However, when it came time to apply ABCD to our community, they could only envision the creation of a database of information that could just be mined. They couldn't make the connections needed between their minds and hearts, so we started heading down the path of community development in name only. It wasn't until one of them attended the Toronto Summer Institute this past season, where John McKnight and some younger field ABCDers were offering a training, that this one person "got" it. Now she's my ally in the work we are attempting.
I don't know Dan; I took my training with Ron Dwyer-Voss a few years ago. Ron is very experienced, having been an organizer, a minister, and an ABCD'er for many years. I see that he includes Dan in the list of stewards, and to me that is a fantastic recommendation. The folks on that list are very committed to this work.