Note: not necessarily saw specific.
I always start by deep googling, most small engines have an exploded parts diagram, sometimes complete with specs for a rebuild. My welding machine for example has every iteration of it over multiple decades as both owners manuals and literally step by step rebuild instructions and specs. Obviously when you get into machining surfaces the price of poker and knowledge goes up, but there are some old school tricks if you research and learn them. For most complex machinery like vehicles, you can often hunt down either chilton or haynes manuals, or go all in and get the actual shop repair manuals (much more expensive but literally walk someone completely through the repair). There are also subscriptions to repair manuals too, so you can have unlimited access to multiple makes, etc. When you take your car to the dealer, that's what their mechanics literally do, they open the file, and then check off each step as they go through it.