What happens when galaxies collide, like NGC-6240, what happens?

Well I believe no measurable change will happen to our solar system. The distance between stars and everything in the galaxy would be still too far apart to anything major to happen. The only differences would be that we would be able to see more stars in our night sky. The solar system might be affected as a whole, it may be robbed if it were to be on the 'clashing' part of it, but nothing big would happen. Its like mixing chocolate powder on a cereal, you would just get more stuff in the area. After millions of years you may see a bit more difference of the shape of the galaxy, but the chances are, our solar system would be unchanged for millions of years, unless it get close to a star, which the odd are very low. less that .000001%. * percent is not accurate, just general estimation.