reliability of the v-12 motor

I have never heard anything bad about the V-12 Mercedes; however, a lot will depend on mileage of the engine, care taken by the previous owner, and your own tolerance for high repair bills. Recently did an alternator job on a 1991 MB300 and the alternator alone listed over $600. They are great cars but parts are not cheap, and finding someone who services them is not cheap either.