if you have oil all over the bottom, an oil leak is pretty certain. But you will never find it with the engine that dirty. Wash it (or have it washed) so that there is no oil or residue or sludge anywhere. Then if you cannot find where it is leaking, get some flourescent tracer and put it in the oil, and use a black light (both available at most auto supply stors) and then you can see where it is coming from.
1st thing to check is the oil filter. If it is a little loose, you will have an oil leak. 2nd most likely cultprit are the end seals under the LIM. (went thru that mutliple times). Most mechanics don't know to put a few drops of gray RTV on the ends of those seals before assembly (not in the manal, found it out from Victor Reinz tech support.)
If you are having problems with both oil and coolant, you either have two problesm, or your problem is in one of the gasket interfaces where both oil and coolant are present. The primary suspects are the LIM gasket, and then the head gasket.