The oring on the egr side seems to be made out of viton or someting similer, (its green). Usually you can reuse it even if its original, however it wouldn't hurt to change it.

Their are three bolts, two attaching the cross over to the manifold, and the third over by the egr.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200