Lauren (and other relative newcomers to the joy of Smalltalk),
you should take a look at http://stephane.ducasse.free.fr/FreeBooks.html and grab some the books offered there. Don't worry, they're all perfectly legal and proper.

The key ones are probably "Smalltalk-80: The Language and its Implementation " aka "The Blue Book",  "A Taste of Smalltalk", "Squeak by Example" ... though most of them are pretty interesting. They are, unfortunately, all a smidge (or more) out of date, and you will have a few moments of "it doesn't look like that on my machine" moments.

Oh, and the (in)famous Byte'81 has a bunch of good articles introducing Smalltalk-80 to the world; sort of the foundational declarations. See https://archive.org/details/byte-magazine-1981-08 And if you prefer video content, try https://www.youtube.com/user/sparaig

More directly answering your question - classes are very cheap and methods are damn near free. Don't fall into the trap of thinking that you should write large methods "to avoid spending time on message sends". *everything* involves message sends; that's why we make so much effort in the VM to make those fast. Modern computers are so fast that things we (for certain value of "us old farts that  used to write Smalltalk on 4MHz machines with 1Mb ram") used to assume were impossible now take milliseconds. I use a Raspberry Pi 4 for my development work and even this tiny $50 computer is staggeringly fast at Smalltalk.

tim
--
tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
Blurglar: cat burglar that relies on speed