I like "Doing Objects in VB 6" by Deborah Kurata. (I haven't read any of the others mentioned.) Many people (the "we don't need no stinkin' methodology" crowd) dismiss this book because the first half discusses methodology and class definition--which is exactly what you seem to want.
Here's a bonus: go to Amazon, search for ISBN 1562765779, and you can order it used for $7.69, which is a steal.