I don't think there's more to using an 8-bit sampler than that either. I picked an old 8-bit sampler open once and it was just an A-D converter and a couple of glue components.
You can find information on the hardware and AmigaOS APIs on
http://amigadev.elowar.com/ though it's pretty much a digest of transcribed docs in bad formatting. At least it's all there.
For more utility oriented Amiga programming I think your best source of help would be
http://utilitybase.com/