That old MacOS stuff is hard to find on the Internet. One thing I did find that gets a bit close is http://www.mactech.com/articles/develop/issue_16/Radcliffe_f.... Problem is that it likely is a bit hard to follow if you do not know about the stuff. Moreover, it doesn't really show patching itself.

I am fairly sure there is some article about patching in those archives of Develop, but I couldn't find it.

Wikipedia has little, too. http://en.m.wikipedia.org/wiki/INIT may provide some starting points.