If you go to the web site for the crate (or the standard library), and find the doco for the module / function / trait / ..., you find an handy "source" button. It will take you straight to the definition.
Yes! After a bit of playing around, I can follow Rust reasonably well... but only with an IDE, which I've never used for C or even really for the bits of Java I wrote. I understand that many more experienced Rust developers are similarly IDE-reliant.
I do think it's a deliberate tradeoff, having e.g. .push() do something useful for quite a few similar (Vec-like) data structures means you can often refactor Rust code to a similar data structure by changing one line... but it certainly doesn't make things as grep-friendly as C.
Eg, (me picking a random crate on crates.io): https://docs.rs/syn/2.0.29/syn/ or the standard library: https://doc.rust-lang.org/std/option/index.html
It's all generated by the same system from comments in the source. You can generate the same thing for your code.