It can be very easy as long as you haven't done a lot of writing to the disk. Here are some steps:
- Make a image of your hard drive partitions with dd, example: dd if=/dev/sda1 of=/home/user/image
- Make a backup of the image and then only do forensics on the image, not on your hard drive because things can change, and be overwritten etc
- If you need to mount your image, mount it as read only!
- Use a forensics tool on the image, such as lazarus, or text you can sometimes recover with strings. There are other tools but I can't think of them right now, start with lazarus.
You will be surprised by how much you can recover with no problems. I will be back to check on your results.