In the online resources section, there's a test you can do on your own. It goes something to the effect of 15 liters (4.25 gal approx) pumped into a container in a specific amount of time. I don't even want to try to remember because my memory is poor, but the specs are there. The pressure regulator under the hood will dampen out pressure fluctuations and maintain a constant pressure in the supply system.
Replacing the fuel hoses is an excellent idea, as is getting the timing chain serviced. I'd also look at the brake lines to see if they're bulging or have cracked. I'd also look at all the fluid levels and replace it all (unless you can point to receipts showing that had been done in the recent past).
Something that stood me well was to get familiar with online parts distributors. When I bought mine, it ran, but not well. As I started to diagnose things that were going out, I was able to find them both online, and at the local Napa, Kraegan and Western Auto parts stores. Some of the online guys are cheaper, and eBay can be your best or worst friend (you can't be sure what kind of quality you'll get sometimes).
Our moderator, GermanStar, rarely lets me down when I need parts, and I have YET to be forced into using the Classic Center or Stealership (both equals EXPENSIVE). Gorgeous though our cars are, they're not "rare" and parts aren't tough to find - you may have to search a little more than you would for a Ford or Chevy...
I'd also recommend getting familiar with posts from this forum - search the thing for threads that'll educate you, and help you find parts or mechanics. I registered in 2006 and find a lot of great gems from Benzworld still.
Lastly, do not resist the temptation to replace Mercedes parts with non-Mercedes parts! The fuel pump/check valve issue I mentioned will cost me the price of a new fuel pump ($600, on the cheap side). When my pump does bite it, I'm going to replace it and the valve with one from Summit Racing (delivering the same volume per minute at the right pressure). I got the idea from a Benzworld thread. Someone here replaced the Mercedes AC blower with one from a Ford Mustang. Etc etc.
Good luck, and be sure to post pics - we like pics