My LCD screen won't turn on.

So last night I bought a new back casing for my iPhone 3GS and I watched a few videos on how to remove the old one which was cracked and replace the new one. It looked easy enough so I started.

I went through the process of removing the bottom 2 screws, pulling up the screen and removing ribbons 1, 2 and 3 before pulling the screen completely off. I was half way there.

I started unscrewing the 7 different screws to remove the motherboard, but a few of them wouldn't come out, and I backed off and just said I would leave it to a professional just in case I made a mistake.

So the 3 screws I removed were put back in, and then came replacing the ribbons into their sockets. I had some trouble putting No.3 back, but then it eventually slid in and I put 1 and 2 back.

My screen won't turn on.. I can hear it beeping every time I put the charger in and out, and it vibrates when I toggle the mute button, but I can't see anything on the display.. I re-opened the phone and I saw that a couple of teeth were missing from the ribbon part of connector number 1 and that the whole connector part of the ribbon wasn't exactly stuck to the ribbon, only by a small thread of something or other. Is it broken? What did I do? Do I need to buy a whole new LCD screen just because of the ribbon? D: