I've got similar symptoms with different fluid and a different tranny. I bought an '83 300CD and let it sit undriven while I worked on the suspension. There were no leaks while it was sitting - maybe the fluid the was low, or maybe it was just happy with the old fluid.

I changed the tranny filter and fluid (Castrol Dexron III) and now I get a good amount dripping from the grid forward of the pan. I think it is coming from the front shaft seal. I've read that the older seals are prone to settling and shrinking if the car is left to sit for a few weeks, so I 'hope' it'll swell shut with increased use and the new fluid. If not, then I'm probably looking at having it rebuilt anyway since I think it's original with no rebuild and 280,000 miles.

If the seals do shrink, the leaks in your "new" car may have more to do with how long it was sitting prior to your purchase than a simple change in fluid.