- Well, it sounds like you have successfully replaced the hard drive, now comes the fun part. You have to install the operating system! :-) You'll need to insert the original DVD for OSX that came with your machine and boot from that. You can also boot from an external drive that has a system bootable partition already installed.
- It almost sounds like your hard drive has died. If you can boot to an external, that would (should) confirm it. Based on your description, I don't think is the system / mother board.
- Here's how I would handle it. Connect everything to the logic board, EXCEPT the hard drive. Try to turn it on. If the machine tries to boot up but gives you the message that there is not a bootable disk found, then problem is most likely the hard drive. If you still get a black / blank screen, problem most likely the logic board.
- If the text messages are important to you, you should consider getting software that can copy them to your computer. After you do that, you can restore as new.