If you have access to the 103 engine manual or CD-Rom, review the section that covers serpentine belt replacement.
Try loosening the alternator and push it toward the engine. You'll gain enough slack to remove the belt. This also comes in handy when trying to reinstall a belt.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.