Drywall work requires three things: the right tools, plenty of practice, and plenty of patience. Tools I have. Practice I have a little. With the tools and my limited practice, I can now put down a reasonably smooth coat, and as long as I don't get impatient (I'm willing to do several thin coats and wait for each to fully set, instead of trying to finish in one day) it comes out just as good as any professional once it's been sanded. I'm just WAY slower - four or five days for a single job.
With that said, I wouldn't advise the average person to try to do a moderately-sized drywall job, because you do need the right tools and a lot of time. You'll acquire the practice in the doing, but it won't be fast. And it's a freaking mess if you're not good. Paying someone to do it will save many frustrating hours and a fair amount of money on decent tools you'll probably only use once or twice.