Thats the kewl thing about OpenGL (and just any 3D API in general). Most of the things you read about isometric stuff are always for DirectDraw. You know why that is? Its because DirectDraw can''t rotate it POV to make it seem like everything is isometric. So basically, you need to treat things like a top-down tile-mapped game (except giving the tiles different hegihts), then rotate the viewpoint.
You know, I''ve been doing an Iso in VB/DDraw, but I was doing someday an Iso in OpenGL.. If you need any help, e-mail me, post here or ICQ on 42699190.. The advantage of OpenGL isometric engine is that you can rotate it, since OGL is fully 3D and Isometric just means the name of view e.g 45% down... Cheers!