Another vote for the smell issue being o-rings in the filter drain. Easy thing to fix. Check out Blackcloud diesel, they have an o-ring kit for cheap.
Next, the oil leak thing is a little nebulous. Where is it coming from? There are half a million different places it could be leaking, some direction as to where it is coming from would be helpful. The most common leaks are as follows:
1.) Turbo pedestal - Leaks behind the engine, around the tranny bellhousing and drips down about where the tranny and engine bolt together. Look slike a rear main leak, but it isn't.
2.) HPO lines - Same results as the pedestal
3.) Rear main seal - Leaks directly from the engine to tranny connection, but not above in the engine valley.
Beyond that, there are more options, but those are first and foremost.