Glad you got it working, Len!
Apple DOES publish some code samples, but you’re right – they’re not always easy to find, and they’re not right there with each method in the docs. Instead, their code samples are in stand-alone projects. I think the intent is to provide enough working code as a base for further experimentation.
Here’s a link to the NSSlider documentation on their web site (probably more useful than the link I posted previously). At the bottom of the left nav are links to sample projects.
Clicking the Mac Developer Library link at the top left of the page takes you to the firehose from which to drink.
Lastly, you mentioned earlier about wanting a “cheat Appendix”. I’m not sure if this is what you meant, but solutions to the exercises are available for download (see “Download Solutions”).
Oh, and welcome to Cocoa! You picked a good time (with the move to Swift rapidly underway) and – for my money, anyway – the right place (BNR) from which to learn. (I’m not affiliated either with Apple or with BNR, except in the latter case as a former student.) Best of luck!