Liz, welcome to the "club". You can go to any Mercedes dealer and buy an owner's manual. I was able to get one my 1980 300SD, it took about 2 weeks and cost only $15. It is a reproduction, but the fact that they still had one available, is impressive. Oil, ohhh the old oil question. I won't go into brands and such. As it has been mentioned above, this subject has been beaten to death. That doesn't mean you should feel bad for asking. there is a search function you can use. When you get a hold of an owner's manual it will tell you what is best for your climate. I do strongly recommend you not go to Jiffy Lube or the alike for the same reason you cited. Yes Mercedes take alot of oil, my car has a 3 liter engine, yet it has an oil capacity of 2 gallons (8 quarts). The "monkeys" at Jiffy Lube would only assume 5 quarts. As for what type, by that do you mean brand or convential oil vs. synthetic?
1994 MB E320 Coupe (199,500 mi)
1992 MB 190E 2.6 (173,000 mi)
1983 Porsche 911SC (148,000 mi)
2004 Volvo V70 2.5T (198,000 mi)
President of CT/Westchester Section