Here's the link to David McCallum's website.
http://featherweight221.com/
I bought both the book AND the DVD and took my grandmother's Featherweight apart and serviced it myself (not my husband, but ME!). I was so proud of myself, but really, it was just so simple. Didn't take long either and my grandma's machine just purrs! I have my mother's Featherweight, too, but I haven't serviced it yet. Another one of those things on my list of things to do.