While the only reason you NEED to learn darkroom skills is if you want to go into wet lab work as a profession, learning the proceedures for processing and developing your film, and printing your negatives, will still add valuable understanding if you also do this kind of work in digital. You will understand where the functions in Pshop came from, why they do what they do, and how they do it. You will also learn what the differences between the two ways of working are, and as a result, when one is superior to the other. Most importantly, however, you'll learn a skill that will be enjoyable for you for the rest of your life, and you'll never stop improving, so you'll have a continuous growth curve.
While you can use the garage, I'd add another vote for the bathroom, or the basement, if the basement isn't too dusty. Usually you have a water source in the basement from the laundry equipment, if nothing else, and a decent sized space to curtain off for a dark room.
D-76 is a film developing chemical. There are lots of choices for this out there, but D-76 is a decent one to learn with. The most important piece of advice nobody has given you yet is:
DO NOT BE AFRAID OF MISTAKES!
You'll certainly screw up your first few rolls of film in one way or another, or even if you don't think you did now, looking back on it a few years from now you'll say, wow, what a mess I made of that... that's ok! Get out there, make some photos, get your hands wet in the chemistry, and have fun!