There isn't a lot to garage doors to be scared of except the springs on them and those to be honest if you are prepared for them aren't bad at all. Ive replaced a couple of doors on remodel houses and if you can follow a manufacturers installation instructions its easy. The springs are nothing to be scared of, read the instructions, watch a few youtube vids so it is clear on how they work and how to adjust them. If you were closer I would offer to help out on a saturday. For the $ you save on doing it yourself you can usually cover the cost of goinng from non insulated to insulated doors and still be under what you would pay some one to install the cheap ones.