Ford 2003 Mustang Workshop Manual page 2783

Remove the bolts and the gearshift lever.
7. Inspect the gearshift offset lever insert and O-ring for wear or damage. Install a new insert as
necessary.
8. NOTE: If necessary, remove the spring and plate for disassembly.
Remove the bolts and the shift spring and plate.
9. Using a 5/32-inch drift and a hammer, drive the split pin downward.