The original poster didn't say what year the car/car kit is and whether the
car kit is integrated factory-fitted or another type.
If factory-fitted before about 2001/2 I agree with your suggestion, though I
didn't think any 3000 series models fit, though some 6000 fit also (but NOT
the 6310i --- grrr).
Any Merc dealer should have the list of compatible phones.
NL/BE are stuffed with Merc dealerships so there should be one very near
If the car kit is an aftermarket one it's more complicated.
NB: To reply directly replace "nospam" with "schmetterling"