Breaking down Rust code into seperate ".rs" files. Is it possible, and if so, does it affect performance?

So I'm working on a windows user interface library and I've run into an issue. My code is nearing 300 lines and nowhere near completed, everything has gone surprisingly smooth, but I've come to realize that the readability of this code is about to go out the window. What I'd like to do is break my structs, extern functions, local functions, and potentially more down into multiple ".rs" files, but I want to know if, firstly, it will slow the runtime at all, and secondly, if it would be exceptionally complicated or simply not possible to do so (alternatives welcome!). I'm focusing mainly on the code itself right now, but because this is something I've never needed to do in rust, I'm trying to find guidance on the process so I can handle this neatly when I start implementing the change.

Thanks in advance guys! :)