Horn And Horn Relay
 

I own a 98 c230 and my horn is gone. Is it easy to replace yourself or it something that a mechanic needs to do? Also, should I start with the horn relay before buying the horn? I have noticed that the relay looks like a plug which seems simple enough but I don't want to mess anything up either.

I would find the horn disconnect the positive wire and using a piece of wire power it from the battery, if it works you can work your way back to the relay or the steering wheel contact. You also could find the relay, take the cover off and manually push it to see if the horn works. I think the ign has to be on

Thanks, peter but any idea where this cover would be? and should I start with the relay first?

I would start at the horn first, that way you can tell if it's the horn itself, or if it's the wiring associated with it.