A: Yes, many LED bulbs are dimmable, but not all of them are compatible with a dimmer, and some dim in different ways. Be sure to choose a dimmer that is compatible to ensure you will get maximum lifespan out of your dimmer and LED fixture.
A: Yes, LED lights burn out, but in general they last significantly longer than traditional bulbs. Typical incandescent bulbs last, or are rated up to 2,000 hours. Fluorescent bulbs can typically rate about 10 times that long. LED bulbs can rate 30,000-60,000 hours or more, and the technology is only taking that further. As your LED bulbs get older, you'll probably notice a fade in the light before they burn out completely.
A: LED lighting slashes greenhouse-gas emissions while saving you money on energy costs in the long term. While LED lighting costs more up front, savings in energy and maintenance more than cover the premium. LED uses less energy, so that's the first green benefit. And because LED lasts longer, you're cycling through fewer pieces and causing less waste. Fluorescent bulbs last longer and use less than energy than incandescent.
A: It's not recommended. The enemy of electronics is heat. LED is electronic technology, so while LEDs put out less heat than traditional bulbs they are more susceptible to damage from heat. You'll notice little metal fins on the backs of your replacement bulbs. Those fins dissipate heat, and LED manufacturers are working hard to make heat less of a risk to the life of the bulbs. But those fins won't help quite as much in an enclosed space. You might find a warning on your LED package asking it not be used in an enclosed space. The biggest issue with heat is that it will cut the life expectancy of the LED bulb.