Nothing is easy in this world, and one has "pay to play"(physically/emotionally/monetarily) so do you have the skin to see this through? Nothing and I mean nothing will be "plug n play"(like most auto shops see it).
A) I would entertain the key/tumbler at the dealer, and find one that has patience for you as some just say "NO". On this key/tumbler they will need for the car to be there at THEIR shop.
B) For them to touch your car. You will need to fix all the mechanical problems with the steering column including landing the wire in its proper place(which sounds like the black wire going to the security module behind the instrument cluster from the key transponder module). Take you 2002 SL apart and it will be the same
C) You hope the dealer can get you the tumbler/key assembly. Get ready to dish-out four-figures ($$$$)
D) Dealer comes back and "Sorry Mike it is no longer available"(not the end of the world)
E) The work of lots of patience is about to begin....
F) Find a locksmith that knows how to make a mechanical key from your existing door and trunk locks
G) Hopefully this locksmith can reset the key pins from a junk (from a junk SL) to re-key it from your existing locks- The car still not going to start-get it......
A) The other option it buy a crashed SL600 of the 98/99 vintage from
or more keys/fobs, and swap over the two-ECU's, one-Security module behind the instrument cluster, one- possibly the RF module for the FOB on the passenger rear quarter panel, and of course the the key tumbler from the column with trunk and door locks...
Understand, that the moment you do this if you need to do any kind of state testing the VIN will not match when they hook up to the OBD port
I'm electronics guy by trade, but someone here on the forum has bypassed the whole Mercedes Security system on a late model SL, and will not elaborate on how it was done, but threw out some "feelers into the air", and good guess is he has a "Julie module" installed.
Understand, that there are four hurtles you need to achieve
A) steering column tumbler mechanical key
B) mechanical keys for the door lock and trunk
C) Electronic key to start and drive the car which has the transponder, or the "Julie" to bypass the transponder...
D) optional remote connection to the car...
Arm your self with a parts list to these cars. Their was a list, but no longer available. I have a condensed version of what EPC has with part numbers and prices from yester years..... You have MB Star, so somewhere there is EPC, and you can see parts break down....
Hope it helps,