Your 3868912 number is neither a serial number or model number. Still not sure which outdrive you have.
You really aren't going to find step by step instructions. You basically remove the outdrive, use a 10 lb. slide hammer to remove the bearing, and using a gimbal bearing install tool, drive the new bearing into position. Then use an alignment bar to set the gimbal bearing to the coupler then check engine alignment and reinstall outdrive.