C230 Transmission Fluid

I am in the process of draining the transmission fluid from my C230 Sport because the maintenance service manual tells you to replace at 39K.  The fluid initally flowed smooth but now is reduced to a trickle.  Additionally, only 1 Qt is in the pan after all night.  I reasoned that possibly the dipstick/filler tube needs to be opened and to my amusement cannot find a dipstick/filler tube.  I have this very expensive transmission fluid, $15 per Qt, one Qt in the drain pan, and cannot find where to refill the transmission when complete.  Has anyone else run into this problem in the past?  Any SME's willing to help a Vet?
Thanks
Bill 

Found it!  For anyone else with this similar problem, remove all the plastic hardware on top of the engine that contains the aircleaners.  The filler cap is located on top of the transmission on rear side of the bellmouth.  It is a small 2" diameter cap that with some difficulty will come off.  It pops off.  I still do not know how to check fluid level.  I am measuring how much is coming out, including what is in the torque convertor and putting that much fluid back.  Does anyone else have a better idea?

I don't think that is the filler.  Does anyone have a clue where the fill port is for a 07 Sport 230 please?

That was it.  Loaded all 8.5 quarts into that little hole.  Thanks for everyones help.  It was very enlighting chatting with the experts.  Thanks again.

Don't forget to drain the torque converter!!