Changed Hard Drive, HD Cable and bought the Upgrade kit
Turned on my Mac one day, and a folder with a question mark turned up on the screen. Tried to reboot and find the startup disk, but the Mac did not recognize that there was a hard disk in the machine.
Turns out that for me it was the hard drive cable that was broken. But I couldn't know for sure. So I bought a new hard drive (750 gb), a hd cable and the upgrade kit that gave me a USB hard drive connector.
I replaced the hd cable, installed the new hard drive and followed the instructions in the guide. After setting up the partitions on the new hd, I rebooted and was able to run internet recovery. While installing Mountain Lion again, the question of whether I wanted to transfer data from another disk appeared, and I connected my old hd with the USB connector, and it worked perfectly. Two hours later, my Macbook Pro was back to its old self, but now with a 750 gb hard drive, and my old one as a backup disk. :)
I learned that it is pretty easy to fix a mac yourself. I the package from Ifixit came a bitset with all the bits you need for the screws on a Mac, and it was easy to follow the instructions of the guide. I recommend doing the same!