My wife's '98 E320 is having intermittent problems starting and brief hesitation when accelerating.

I bought the car used a couple of months ago with 62K mi. It was missing the service records, but appears to have been maintained. Regardless, I've been doing all the Schedule B and AP service myself so I have a good baseline.

About a month ago the check engine light came on, but the car drove fine. A shop said it indicated "fuel trim" and reset it. They said to bring it in if it happens again.

Yesterday, my wife had problems starting it. It would crank, but not start. After repeated tries, it started right up like normal. This happened twice in one day.

I haven't been able to duplicate the starting problem yet, but did notice some hesitation once while accelerating.

I'm guessing I have a fuel delivery problem, but I haven't found a source for service manuals for a W210, so I'm not clear how to proceed. I replaced the fuel filter a few weeks ago. Can anyone tell me the procedure for replacing the fuel pump and fuel sending unit? If they are easy enough, I'll try them first before I take it to a shop.