I believe that is the wrong part. The correct Mercedes number is 170 545 03 05.
However, what many have used here in the USA is Standard Brands relay Ry 1562; That is the correct replacement for a Crossfire and the Mercedes SLK 320.
When looking for the Standard Brands relay for a 2003 SLK 230 the number referenced is Ry 1739. Which indicates to me a different relay requirement.

After I dug deeper at the Standard Brands website it lists the Ry 1739 for both the SLK 320 and the SLK230, So apparently the two are indeed interchangeable.

It would be best to start a new thread and tell us exactly what is happening with your car. Does it turn over when you try to start the car or nothing at all ? What happens after you relax the key one notch counter clockwise from the full start position and let it there for one minute; Will the fan start up to high speed ? etc the more info we have the better we could help.