I just converted my iphone yesterday with a transparent front and back. The first thing i noticed was the picture quality of the camera. the performance isn't hindered in any way, but because of the transparent plastic, the pictures are just a tad bit fuzzier than normal. it's hardly noticeable, though, unless you're looking for a difference. overall, i really like how my phone looks and the picture quality doesn't bother me at all. like i said, barely noticeable. also, the flash works fine as well.
The first cable might be loose. This connects the LCD. I would first recommend reseating this cable, and it might work. If not, then you would definitely need to replace the LCD in order to have a working iPhone again.
okay, to solve your first problem: the proximity sensor is what tells the phone to dim during a conversation. I would recommend to reseat cable three securely until the white line on the cable is almost touching the connector your second problem: opening your iphone while it's on could cause it to short. always make sure it's off before opening it. I would recommend to reset it by holding the power and home button until you see the apple logo. If that doesn't work, try restoring it. Hold the home button for a few seconds and insert the USB cable while itunes is open. This happened to me once. I let the phone sit for two days, didn't touch it, and it ended up turning back on for me.
This might work for you: fill up a zip-lock baggy about halfway with white rice and submerge your iphone in it. Make sure you seal the baggy correctly. The rice should soak up the excess moisture. This has worked for some people, so it might work and it might not.
If the iPhone wasn't like that already before you replaced the LCD assembly, it could be one of two things: either the store you bought it from sent you a faulty LCD (it could've been handled roughly in shipping, too) or the first cable isn't connected firmly. However, it's probably the former, if the LCD wasn't connected right, it would show nothing but a white screen. Take out the cables and try to reconnect them and see if that helps. If not, I would request a replacement.
No, the 3G and 3GS displays are not interchangeable. You most likely have water damage to the logic board, more specifically, water damage to the 1st socket. I've had this happen to a friend. We bought a new LCD and installed it, and the problem still persisted.
Pry up the assembly again and check where the home button is. There should be two small gold prongs protruding from the assembly. These come in contact with the two other gold strips where the dock connector is. If the prongs are missing, then that's your problem. These break off easily and you might have not even noticed.
Depends what firmware you have. If you have iOS 4 already installed, then you're out of luck, sorry. You'll have to wait a while for it to be released. But if you have 3.1.3, then use spirit to jailbreak and ultrasn0w to unlock.
I had the same problem with my 3G. What I ended up doing is buying a new headphone jack to replace the old one. The button that the power button knob presses against is attached to the headphone jack. I bought it for about $9 on eBay. The power button functioned again after installing the new headphone jack. The guide to do this is found on the ifixit website.