Just a couple of questions

Ok, so the interior of my cave is coming along really nicely, but the exterior lighting isn't really working out. I've created somewhat of a concealment for my cave entrance (rocks that make it not so square), but the lighting isn't working out. I made a large spot light for the "sunlight" that I want coming from behind the mountain (NURBS cone) that contains my cave, but instead of creating a shadow of the mountain, the light goes through the cone and messes up all the interior lighting I have for the dragon's lair. So, my question is, any suggestions for this?

My next problem is with modeling the exterior. I want to have trees, but the "pre-made" visor trees take too long to load and scale properly. I tried to think of a way to model a nice-looking tree (at this point, I don't care whether it's hardwood or not) and couldn't come up with a solid design. If you haven't already figured it out, I'm best at NURBS and am not used to polygon modeling. However, if you have any polygon or general tree tips I'm all ears. It's the learning experience I'm going for. New stuff isn't a bad idea. Thanks.