mixyIt's not too hard, with the right tools. I wouldn't use a Radio Shack soldering iron though; a decent Chinese clone will probably run ~$45USD, but most recommend a Hakko 888D. You'll want a good iron, rosin-core solder (~0.03"), tip cleaner, and wicking mesh/solder sucker for mistakes/cleanup. Practice on some junk PCBs until you're confident you can get clean joints.
There's a lot of video tutorials on Youtube if you're interested.
mixyReally easy but you do have to be careful, also the equipment can get kind of expensive (I spent about $200 on soldering equipment, because I wanted to make sure I had good equipment and was fully prepared, and wanted to solder lots of keyboards). If you only want one board and have no other use for soldering tools/skills, you might be better off finding someone on GeekHack, Reddit's MechMarket, or elsewhere to do the assembly. People do it for very reasonable prices.
JJDWYou can even build them with a $15 soldering iron (15Watts). But as you have said, it is very easy and there are plenty of tutorials that explain really well how to do it.
ZambumonThe problem with cheap irons is that they usually use cheap tips (I've had these melt before the solder a few times, haha) and the lack of temp or even wattage control can cause problems (too hot can melt leads, too cold gives bad joints). It's definitely doable, but I wouldn't risk it on an expensive PCB when you can get decent Chinese clones for a bit more.