How long does it take to write a compiler

Compile time dropped from 3 hours to 7 minutes.
Well, file access sure has a hand in this but as jalf said, the main reason for this will be something else, namely the repeated parsing of many, many, many (nested!) header files that completely drops out in your case.

Generally speaking, there's no five minutes tutorial for compilers, because it's a complicated topic and writing a compiler can take months.
You will have to do your own search.
Python and Ruby are usually interpreted.
Perhaps you want to start with an interpreter as well.
It's generally easier.

It's also OK to write different stages of a compiler in different languages, if needed.
Your entire language should be covered by test cases; effectively it will be defined by them.
Get well-acquainted with your preferred testing framework.
Write tests from day one.