Price of Swap for VR4

Hey I new to this but I really have a question about my Galant. I have a 1999, 4cyl but it really doesn't hold weight on the street. I would like to know what should I be expecting to spend to swap the motor with a VR4 motor... and if it is even possible. I would really apprciate some input, I know it is going to be costly but I would like to know how costly.
Also what is the difference between the VR4 and the VR6???