I have a 2000 C280 and i'm in the middle of changing the water pump. The new pump has two gaskets that came with it. One looks like the original one that fits in the groove and is slender. But I got a second one that is flat with marks the size of the slender one. I'm wondering what to do with it. Should I use both or what?

I was also wondering if I should use gasket sealer. I have some black oil gasket maker I was going to use.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)