Eric, no need to change all locks.

First off, Benzmac advised me 1-2 yrs ago to change out the tumbler AND the steering lock mechanism at the same time, when my 300D had this problem.

My indie decided that it was best to only change the tumbler.
Soon after, it got stuck again. So the mechanism was changed also.
Now no more problems
The tumbler can be rekeyed to your original key. Buy the tumbler and take it to a locksmith (one that does not break things)
It can be rekeyed to your original key.

Have the locking mechanism hanged out.
Other members have had varied experience with just changing the tumbler only.
Benzmac has more experience!!!
It worked for me the hard way.

sorry to hear of the problems. hope the locksmith did not charge you.
try to get a pithing needle from a bio lab or a sharp pointy pick. maybe you can coax the key stem ou.
have a needlenose plier ready, a fine point one or a doctor's
locking 'plier'.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD