I've visited the website mentioned on mbnz.org myself as well and I don't know whether these "xenon lights" are to be considered good or not.
On this internet page is claimed that all necessary parts and wiring are included and installation will take 45 min "DIY"...
I presume that it is well known that the OEM headlight units and lenses for xenon are different from the standard ones. Just take a look at the W210 E-class and the difference can be seen right away.
I don't know what the US DOT regulations are about these xenon lights, but in Europe you are only allowed to have them in combination with headlights washers/nozzles.
The total package mentioned on http://www.xenonhid.com
does not contain any parts or wiring for the C-class headlight wipers.
For a C-class you will need additional wiring, waterpump, hose (or however it is spelled), (painted) trims underneath the headlight units, and wipers with nozzles.
Even after visiting this page with the cheap "xenon-like" bulbs, I do not consider it worth the effort (like others already wrote as well).
You can have the lights upgraded by the dealer....