example scripts

There are many scripts in the doc area
http://sikuli.org/documentation.shtml (available in Sikulis help menu)

and in the blog
http://blog.sikuli.org/

and here you can find 2 of my examples
http://sikuli.org/trac/wiki/RaiMansExamples

Using images in more than one script:
you can build an image repository (a directory containing your images) and use it in your scripts by setting the path to it by setBundlePath(Full-Path-to-Image-Directory).
In this case you have to take care for your captured images your self (move/rename them from the scriptfolder to the repository - no further support yet in Sikuli)

header file:
Sikuli does not work with header files and even does not have its own import/include function.
I have a basics.py, where I have some basic def()'s and global constants, that I activate in every relevant script by
execfile("path-to-basics.py")
e.g. a function that opens a given page in the browser and waits for completion.

Pls. take care for your other questions and react accordingly - e.g. set them to solved.

solved