How handy are you with moderately complex mechanical systems? If you are handy enough to adjust the brakes or shifter on a bicycle (with instructions), you are handy enough to take apart and maintain any of these, IMHO.
Having said that, of the 3 rifles (mini-14, AK, AR-15), the mini-14 is probably the least intimidating mechanically, the AK is
slightly more complex (almost as simple as the mini), and the AR-15 is the most complex.
You can download instruction manuals for the three rifles at the following locations:
Ruger mini-14:
http://www.ruger-firearms.com/Firearms/PDF/InstructionManuals/55.pdf
AK (SAR-1 and Vepr used as an example, but all work the same):
http://www.ar15.com/content/manuals/SAROperationManual.pdf
http://www.ar15.com/content/manuals/vepr.pdf
AR-15:
http://www.ar15.com/content/manuals/manual_bushmaster.pdf
http://www.ar15.com/content/manuals/manual_olyarms_ar.pdf
Look through those and you'll see what I mean. The AR is by far the most intricate and has slightly more complex controls, and takes a bit more mechanical ability to take apart and put back together. The AR is also a bit more temperamental, in that it is more likely to jam when dirty or unlubricated than the mini and AK.
The AR is the easiest of the three to shoot well; has by far the best iron sights of the 3, if you're not going to be using optics; and is the most accurate. The AK and mini-14 offer somewhat less accuracy, but still decent once you get used to the rifle. All 3 are easy to mount optics on (assuming you get an AR with an optics rail instead of a fixed carry handle), and you can buy optics for the AR and mini at Wal-Mart (AK optics will probably have to be mail-ordered).
Without optics, the AK is definitely the hardest of the 3 to shoot well, due to the short sight radius. However, I have a Kobra on mine, which makes it much more user-friendly. It is not inherently less accurate than the mini, IMHO, but in the hands of a newbie it probably will be, as the sights are not particularly user friendly.
Good magazines are very easy to find for the AR and AK pretty much anywhere, somewhat harder for the mini. Ruger only sells 5-rounders, so you have to hunt for aftermarket mags that work well. They're out there, though, and THR can point you toward vendors of mags that work.
The AK recoils a bit more sharply than the mini-14 and AR-15, but it's still mild as rifles go.
For someone who is new to firearms, the mini-14 would probably be the easiest to get up to speed on. If you don't like the straight stock, you can get pistol grip stocks and folding stocks (I had a
Butler Creek folder on my mini). The AK isn't hard to learn to operate and maintain, but may take time to learn to shoot well. The AR is most challenging from a mechanical and operation standpoint, but probably the easiest to learn to shoot well.
The SKS is roughly as complex as the AK and a little easier to shoot, but is bigger and heavier than the above 3, and the magazine is non-detachable.
The bolt-action milsurps are EXTREMELY simple to operate and maintain (to "disassemble" a Mosin-Nagant, you merely open the bolt, hold the trigger down, and slide the bolt out of the back of the receiver, and you're done), but they recoil a LOT harder than the mini-14, AK, or AR, which may make them harder to learn to shoot well since the recoil can be intimidating. Some of them are dirt cheap, though.
Hope this helps!
