You might get the dealer to do the seals for $550; no way they'll also do the guides for that much as the cyl. head requires removal for guide work. Head can be left on for seal replacement.
Alot has been said on this subject, especially at this site.
It's my understanding that the 2.3 motor is an M102 - 4 cyl. If so, that makes it 2/3s of an M103 motor - same basic engine design.
Randy Durrance, a veteran MB mechanic who used to participate here once said that M103 motors guise oil consumption - you won't necessarily see oil-fouled plugs unless the consumption is enormous.
In a previous post, Benzmac said you would not see oil on the plugs if the leakage was thru the exhaust valve guides.
Bottom line - you gotta tear it down and have it analyzed to know for sure. If the MB dealers 800 miles per qt. thing is right and your plugs are dry, exhaust is not smoking and car runs good, you may just decide to live with it.