i will try to post a pic of my jeep later today if i can... i'll go take one since i don't have any real recent ones. i have some aftermarket flares on mine though which give more room (along with the 2-3" of trimming that was done), and i also only have 30" tires on it... so as you will see, i have a good bit of extra clearance.
you should be fine with a 3.5" lift... no major issues. you will at least need to lower your
transfer case by 1/2" to 1", but this is easy and inexpensive. i would definitely agree that anything over 4" will require more modifications though. however, even with a 3" lift its possible that you will experience some problems if you don't make adjustments to compensate for the lift. my jeep did fine for almost a year with nothing other than the t-case drop, but then it began to develop the infamous "death wobble"... likely due to components wearing at an accelerated rate. now i have an adjustable tracbar, adjustable upper and lower control arms, a heavier duty steering stablizer, etc. hopefully you wouldn't have to do all that though.
31's will probably fit fine with the 3" lift, but you might experience some minor rubbing on full articulation or if you turn the steering wheel all the way in one direction (depending on what backspacing your wheels are).
DO NOT get AAL. you're only looking at an extra $150 to get full springs from rusty's. if you're really pressed for money, shop around and see if you can find something cheaper, or ask some other people on this board about other options (taking springs off other vehicles from the junkyard... for example).
good luck... you'll love your lifted jeep.