The only oil leak on E90s that is not to be trifled with is the oil filter housing gasket. If that is even seeping a bit, it is very important to replace. The oil pan will not drip on anything other than your under tray and potentially your driveway/garage. If it is just “seeping” I would say you’re fine to let it be until it starts to actually leak.

The front control arm/thrust arm bushings are pretty important to take care of and they typically go out around 70-80k miles. I’m not sure if you’ve noticed, but when they’re worn you will feel a shimmy/vibration in the steering wheel under braking and the on center feel of the steering will be very loose. One of the best handling modifications for these cars is the M3 front control arm upgrade. FCP Euro sells a kit for a little over $300 and it tends to be much cheaper than new non-M control arms. Labor would be about the same to install.