haha, yeahhh, I could find something from beethoven, mozart and so, but no Rachmaninov... this guys is sooooo crazy good it's amazing, Bought me from David Helfgott a CD, he is playing Rachmaninov and since this day, I am addicted in that kind of music.

Now I would like to try playing on the guitar. But I never could see that on guitar, maybe it's impossible ?

If you were to attempt it, you would have to get the sheet music. You need some arrangement skills and understanding of theory if you want it to sound good.

The piano parts are what you'd be looking at, especially if you are attempting to perform it s a solo piece. The upper melody is the most recognizable, so you should probably focus on that. If you are performing with others, you can distribute the "left hand" parts among them.

A piano lets you do different things than a guitar, so might have to simplify some parts. Also, you should carefully consider what techniques (legato/tapping, picking, etc) will suit the piece best.