I hope that you don't mean that you were getting ripped off because you had to pay to get your car serviced. We have purchased several tens of thousands of dollars in tools to properly repair Mercedes autos.
That aside, you will need a 1/4"drive 5mm allen socet, a set of extensions, some specail pliers to remove the boots without tearing them. That is to get off the cap. To replace the rotor, you will need a 3mm allen made by Hazet so you will not round off the internal corners of the bolts. IF you do, you will have had a bad day.
Good luck with your trials. and errors.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM