First check this: One of the 2 bolts that supports the crank reference sensor bracket is a very common leak on m30's. Here's more info: http://www.evansweb.info/2003/02/19/...gine-oil-leak/
Another comment: I did mine on my 87 535is, and I am not a professional. I did have to make/fabricate a big beefy bar that I could bolt to the front of the crank to hold it still by letting the end of the bar wedge on the ground, and after i destroyed two 1/2 breaker bars and borrowed a 3/4" breaker bar, it was not bad at all. I have heard it may not be good for the engine to use an impact on the nut, so I didn't. Some others may know better about that.
Front oil seals - renewal
M10 and M30 (timing chain) engines
Camshaft front seal (M30 engines only)
1 Remove the upper timing chain cover only (see Section 7).
2. Support the cover on two blocks of wood, and drive out the seal from behind with a hammer and screwdriver. Be very careful not to damage the seal bore in the process.
3 Coat the outside diameter and lip of the new seal with multi-purpose grease, and drive the seal into the cover with a hammer and a socket slightly smaller in diameter than the outside diameter of the seal.
4 The remainder of refitting is the reverse of removal.
Crankshaft front seal (M10 and M30 engines)
5 Remove the crankshaft pulley and vibration damper (see Section 7).
6 Carefully prise the old seal out of the cover with a large screwdriver. Be very careful not to damage the seal bore or the crankshaft with the tool. Wrap the tip of the screwdriver with a piece of tape to prevent damage.
7 Clean the bore in the cover, and coat the outer edge of the new seal with engine oil or multi-purpose grease. Also lubricate the lips of the seal with multi-purpose grease. Using a socket with an outside diameter slightly smaller than the outside diameter of the seal,carefully drive the new seal into place with a hammer (see illustration). If a socket isn’t available, a short section of large-diameter pipe will work. Check the seal after refitting to be sure the spring around the inside of the seal lip didn’t pop out of place.
8 The remainder of refitting is the reverse of removal.
http://www.e34.de/tips_tricks/haynes/02a.pdf