Lucky for you, Living Legends does indeed include joystick support. In fact, you shouldn't even TRY to fly the aircraft without one. This is because if you don't have one, you are currently locked into having the standard inverted flight mechanics on a mouse (you lose pitch controls for some reason if you try to invert it - a workaround is flipping your mouse around). However, this is peanuts compared to the fact that your mouse x axis, rather than turning you, rolls the aircraft. The keyboard does the turning, which is practically useless because you can't aim for crap with the keyboard. Basically, combine all of this, and you get a control scheme that will endlessly confuse you. Precision aiming with inverted pitch (on a MOUSE) and an oversensitive roll is pretty awful.
Yeah, it's a really fun mod overall, but it's also extremely demanding for your computer.
I'd say you'd need a tri-core processor at the MINIMUM. You can try using a dual, but you will certainly have performance issues no matter what your graphics card is, unless your clock rate is absolutely rigged (more than 4ghz). And a graphics card at the level of HD 4870 or 9800 GTX+ for basic medium settings. This mod is nothing like the Crysis campaign. You probably need to get an HD 5870 or GTX 480 to get smooth framerates at the highest settings.