Yes, it will decrease the distance... I won't give you a rule, but as a rule... (just kidding)... in general it's several yards or more, depending on a whole bunch of factors -- primarily wind. Putting backspin on the ball makes it fly higher (topspin does the opposite), so the ball will be more affected by it. Thus, putting backspin on a downwind drive, for example, will actually make it go farther (and stop more quickly).
On a flat surface, with no wind, my 60 degree wedge goes about 86 with no spin, 81 with full backspin. But add in all those other factors, including green speed, lie and the slope of the green, and it will change. You're going to have to experiment.
Topspin can be helpful at times. I use it mostly at St. Andrews, where the ball will roll forever, especially into the wind. Play practice rounds and mess around with both spins, and degrees of spin, with all kinds of clubs and shots (your score won't count).
EDIT: It's true that you need the right clubs and balls to get spin. However, moving the aim dot up or down the ball will still change the trajectory of the ball flight, so a starter 7 iron with a starter ball and full "backspin" will go higher and roll less than the same setup with no spin; and topspin will make it go lower and run relatively more.