Fallout 3 is the first fallout game that i've played and i'm a bit unsure of a few things. Some of these may seem like stupid questions but we all gotta start somewhere. C'mon help a noob out

1) Radiation. I got radiation sickness before but didn't notice it have much of an affect. What exactly does radiation sickness do?
2) Is there any way that i can repair my own equipment rather than pay someone to do it? What items would i need?
3) I got the suite in tenpenny tower and one of the things i can buy for it is some sort of chemistry station. Will this allow me to cook up my own chems? (psycho, jet etc). If not what can i cook up with it?
4) Finally what, if any, guilds or factions can i join. I would assume since this game is fairly similar to oblivion that i can still do this?

Any help is appreciated

1) Decreases stats.
2) Need Misc items?
3) Yes
4) Brotherhood of Steel?