get the grimrock model toolkit, I don't know the oink but look around the forums and you'll find it, it can put on custom textures to models and convert them to the format used by grimrock.
You'll also need a program that can convert images to DDS format, I use paint.net to do this but there are others too
The GMT has come a long way since that tutorial, so a few of the menu prompts and button pushes might be different, but nothing has changed fundamentally.
My Grimrock Projects Page with links to the Grimrock Model Toolkit, GrimFBX, Atlas Toolkit, QuickBar, NoteBook and the Oriental Weapons Pack.