Oil filter housing gaskets are likely leaking, its very common on the N51/52/54/55 engines. The gaskets are pretty inexpensive and most mechanics will charge 2-3 hours to replace them. If you have a little mechanical knowledge you could do it yourself.

As far as the trans goes, use a diagnostic scanner to check for any stored faults in the EGS module, other than that and "feeling" how it feels there is no way to know what is going on inside of it.