1993 BMW 525 93 525 BMW--Leaking Fluid

1993 BMW 525 Engine Size unknown Wheel Drive Type unknown Automatic 158000 miles

I just came back from a vacation and drove my car for the first time in a little more than a week. After driving it once, I noticed a small amount of fluid under my car, but couldn't tell if it had come from my car. However, today I saw the fluid again and actually saw it dripping from my car. My first guess is that the oil is leaking as the fluid is almost clear and relatively thin, but I am not sure. I am about to go on a big trip, so I am planning on taking it to the mechanic, but does anybody have any advice about what it might be? And how complicated and expensive it would be to fix?

Thanks!