so far in my entire time playing minecraft i think ive found about....6 slimes. 3 were little in a cave i found, i got bored and killed them. one was my first slime ever, but he was stuck in a wall so i tried to mine him out and accidentally killed him. 1 was found at my doorstep, which is NOT subterranean. and another i found just today deep in a cave. this forum needs a slime smiley!
Yes you can. Normally they are rarely near the lava levels.
Here for example though, someone brought a big one up to do battle on the surface:
I normally just use the diamond sword though, to take him down in one foul hit.
99 arrows?
Take mine. I've got hundreds.