What exactly do I even need replaced!?

I bought a 32gb iphone 4 (and 8gb 3g) today for $60. The screen on the iphone 4 is cracked but the person I bought it from said that it did work. I was worried when I plugged it into my computer and itunes wouldn't find it but after charging it with a wall charger for awhile, it appears that it was just extremely dead. However the screen still did not power on but at least I know the phone does work once it was charged enough. After looking at the phone I noticed that it had definitley been taken apart previously but I'm not sure how far apart so I don't know if the person just didn't put it back together right or broke something. I live in a small town so the closest iphone repair place is about 2 hours away. I was looking into the werx screen replacement thing where you send it in but at this point I'm not sure what I need replaced. Any ideas? Suggestions on where to get it fixed?