Hi Rick, that model number doesn't bring up a manual though the parts diagrams are still available at Sears Partsdirect. There is a decal of the belt serpentine under the left footrest. Set the parking brake to release tension on the pulleys. Start at the transmission and work forward. From a similar model manual (page 23 below):
TO REPLACE MOTION DRIVE BELT
Park the tractor on level surface. Engage parking brake. For assistance, there is a
belt installation guide decal on bottom side of left footrest.
1. Remove mower (See "TO REMOVE MOWER" in this section of this manual.)
2. Remove belt from stationary idler and clutching idler.
3. Pull belt slack toward rear of tractor. Remove belt upwards from transaxle
pulley by deflecting belt keepers.
4. Pull belt toward front of tractor and remove downwards from around engine pulley.
5. Install new belt by reversing above.