Have this car that I love, but hard to love when it doesn't start.

Key goes in OK, but will not turn the tumbler. It had been getting tougher and tougher to turn this thing over the last year or so, and should have taken care of it sooner. In my W124, it was a cinch to replace the key and tumbler but not sure on this model. For those that know the type of key and tumbler I have here (see pic), my questions are:

-If I can ever get this guy to position #1, can I just replace the key/tumbler combo like I did on my W124? I have heard some of these are more complicated with some transponder module (what is that and where would it be?). Do I really need the special tools that I see in some of the posts, or can I improvise?

-If I cannot get this to position #1, am I looking at the huge, time consuming task of cutting up my ingition system under the dash as has been described in other posts?

-Another route is to get a new key for around $200 at mercedes. This seems a risk, as if the tumlber is also worn, the new key may not work. However, if it does work, it would probably allow me to replace the tumbler before things get worse without the big under-dash work, so the the $200 may be a good gamble.

Any input is greatly appreciated!!

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Treiberg's Collection: 1981 240D, 1985 300SD, 1992 300E, 1997 E300D, 2005 C230K