Adding SSD to 21.5"

I am looking for any advice that could help before I have to open it up. I don't want to go in blind and figure out I need some kind of cable, etc.

Has anyone else ever done this before or seen someone post about doing it somewhere else?

I searched and the only info I could find was on 27" models.

Anyways, I have a 2011, 21.5" iMac (base) and want to keep the superdrive if possible, but I won't lose any sleep over it if I can't.

ALSO, any SSD suggestions would be appreciated! I'm looking for 128 gb but my point of view on the ssd is any will be better than the hdd.

ANY info would be appreciated!