Do you have the 14mm allen head socket? Forget an l-shaped allen-head. You'll need leverage.
Auto-Zone sells a set which includes the 14mm; othwewise you get to go see Mr. Snap-On and when I bought mine it was $21 for a single 14mm allen-head and that was 6 years ago.
Above advise about removing top plug first is good. You could be in a mess if you drained and then couldn't refill.
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.