disp terrain:
create a brush. I like to start out with a 128 or 256 block. Click on one face and then go to the disp properties in the texture tool and click create. You can choose from 2 to 4 for how dense you want the mesh to be. To create a large section of terrain you have to turn multiple brush faces into terrain and then sew them together. To do this, you have to make sure the world brushes the terrain is created form is aligned perfectly with the edge of the other brush. Then select both faces and hit sew. To push/pull the terrain, select the meshes you want to modify while in the disp texture tool and use the brush tools available to raise or lower the terrain. You can also create noise and smooth. Terrain does not block vis, so you will have to create a brush underneath it to control that. amnother cool thing you can do is subdivide, which is very useful for creating caves and tunnels. try making a hollow cube, with all the faces on the inside meeting the other edges of the inside face edges, then select the interior faces and turn them into terrain and subdivide and it will smooth all the faces into a spherical shape. I've created entire cave levels with this process wich turns out pretty cool, though controling the vis is a bitch and the general process is pretty cpu intensive.
light_dynamic: this is the only way to create a dynamic light in source. It works like a light_spot, and has a max distace that shows up as a sphere to show how far the light will affect things. The bigger the sphere and the more faces it effects at once, the more expensive it is. You can parent these to physics objects or pretty much whatever.
There isn't a stock light ray effect in source. The only two ways I know of to fake it is with a model, or stacking glows that start small and bright at the light source and get bigger and more transparent as they get farther away.
I didn't know about the showbudget thing, I'll have try that out at work, maybe it's something they added recently.
I haven't ever tried to open any old rmfs or load wads in the new hammer, so I don't know how to address any crashing issues. The source maps are vmf's not rmf's.