You shouldn't have to start a new project in order to use the default code. What I would do is simply edit the default code. Don't change any folder or file names. The compiler can't handle long file paths, so for best results, place the folder with your code on the desktop. This will make the source file name as short as possible. As long as you don't change any file paths the code should compile.
As for the errors in your code, what sort of errors were they? If there are syntax errors, you can double-click on the error given in the compile window, and MPLAB will show you about where the error is. If the error has something to do with a file path, follow the directions above.
Let me know if this helps!
