Questions on trd lowering springs

[Nictheguy]

I've been looking into the trd lowering springs and I'm pretty confused. I'm new to modding and this would be my first mod. First question, will I need to also get the trd sway bars to run the springs? What are the consequences to not getting the sway bars? Also, searching around on amazon and ebay I have found that there are two different part numbers, is there a difference between them or am I just over thinking it? Also, what is the pricing? On ebay they are $200. On amazon they are $240 and that says all four are included, though on ebay there is no info on what/how many are included unless I missed something and I'm over thinking it as well haha. Finally, what is the drop? I've heard it's .75 and also that it is 1.5 inches, I'm kinda going for the inch to inch and a half (if it even matters lol). Thanks for the hep in advance