It was very difficult but I was able to create a video that was almost indistinguishable form an origional about a year ago. Unfortunately the computer it was stored on crashed. I was able to recover it but the quality was never the same. It took up over 300GB and since it was practically ruined, I just deleted it. If you want, I could tell you how to make an actual video. The requirements are as follows:
a computer with at least 300gb free space to store a 1 hour video (when you are finished, you can convert the video to avi and have it take up less than 1gb. All of the programs create files that take up like 20X more space than they need to)
3.6ghz or higher genuine intel processor
2gb ram
Photoshop 7.0 or higher
an image enhancement and blender software
an jpeg to mpeg - 1 conversion program
an mpeg - 2 to avi conversion program
a vocal pitch adjusting program
a light to dark image converter
a video splitter/joiner software
a program that syncronizes the background with the images (can't remember name)
There is a lot more stuff you need but I can't remember it all. Personally, it wasn't worth the nearly 5000 hours I put into it. It was perfect though. I could have gotten it done faster with a team of assistants! Maybe then it would be worth it! Another thing you need in order to do this is A LOT of patience. I set up my own area outside where I could smash glass bottles with a bat so I wouldn't take it out on the computer. I would have to say the characters voices were the most difficult of them all. I had to turn a sentance "I thought we were your best friends" into "we are all freinds". It was extermely difficult to turn cera's jelous, angry word "friends" into a nice, heartfelt word. It is possible but if you arn't prepared for this project to take well over a year and a boatload of disk space, don't start it. Also, the program's required for this would probably cost well over $2000 but if you wan't to start, I'll give you the registration codes so you can get started for free.