If washer has been idle long, or and older model very delicate job. If not (see blowup in http://www.appliancepartspros.com and give it your movel and view diagram 11) and follow.
Note position of belt before removing pump below:
Remove drains hoses
Remove 4 screws holding motor to base
Move motor inward while removing belt from idler under tub
Remove three screw holding pump to motor--delicate removal of pump
Reverse above and good luck
Srolot, November 2007