Able to replace the CPU
I finally upgraded the CPU by myself. Just un-screw four screws on the heat sink, cleaned the thermal compound on the bottom of the heat sink, removed the old CPU, installed the new one, apply new thermal compound (artic silver), re-mount the heat sink and screwed in the four screws.
Windows XP abled to detect new FX CPU and updated automatically. After the system restarted, everything is perfect. I don't have to ship the unit back to Sager for upgrade and risk shipping harzard. I'm glad that I did it myself.