I was wondering how i could use blender to create simutrans vehicles and buildings.
If you know how to use Blender, you just need what we call the master scene to start creating objects. You have all details about how to create that sample scene here (http://simutrans-escala-real.blogspot.com/2008/09/basicos-de-blender-la-escena-bsica.html) (it's in spanish) In addition to that, there're several basic blender files at graphics.simutrans.com, with a master scene set too (link (http://graphics.simutrans.com/thumbnails.php?album=30))
On the other hand, if you don't have blender skills, the first thing you need is a good manual
Anyway, this article (http://simutrans-escala-real.blogspot.com/2008/08/creacion-de-un-objeto-para-simutrans.html) explains briefly all steps you must follow to create an object with Blender for Simutrans (it's in spanish too)
I can also help with providing examples from pak128.Britain if you would like, but then you will end up with objects using pak128.Britain lighting styles, which may not be what you want if you want to create for other paksets. A good tutorial in English for blender can be found here: http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro
Well, the master scene set is focused mainly on the camera and tile position because as you said, lightning depends on the pakset.