The timing chains on the M103 motors(89 300SE) are known to last a LONG time. If you've done 3000 mi. oil/filter changes and haven't driven like a moon shiner, I would doubt your chain needs replacing.
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.