Damn, you move fast, mikes72t!!!
My dad once owned a 240D with over 360k miles on it. Dunno if the engine was original, but the doors still closed with authority. I do not believe any car since then is built to such tank-like standards.
I recall reading that a mix of regular diesel + biodiesel (B20???) burns cleaner than regular diesel fuel.
I'd personally like to run WVO in the Dodge 2500 with 5.9L Cummins, but I'm cautious because I rely on the truck daily.
Mercedesshop.com has good forums, and I like Rusty at
http://parts.mbz.org/ for parts.
Look at greasel for information about getting WVO from restaurants. They recommend going when the restaurant isn't busy. Check the WVO vat first. If the oil is nasty, go to another restaurant. If the oil is clean, ask the manager.