Oil line leak 95 volvo 940 B230FT engine

[tolian2]

When I was checking the car prior to purchasing my mechanic told me that I have the oil line leaking (not turbo related). It was in February.

Couple of days ago while changing oil another mechnic showed me one really greazy/oily hose which was under the engine on the front passenger side. He said that someone put a cheap aftermarket hose and that is why it was leaking. I think I loose about 1 quart about every 2000 miles or so.
It's not that bad but I'd still like to figure out the problem.

Could it be the oil cooler hose? or are there any other hoses that have to do with oil transfer/delivery to/from the engine.

Also how to make the job of changing the hose not too messy. Would I need to add a lot of oil after I'm done with changing it?

Thanks,
Anatoli