If the filter was plugged, the fluid would be coming out of the dipstick tube, for the tranny. I would suspect the pump has went out.
If the pump is not pumping the fluid through the case, that means it's all in the case. Hince the overfull condition of the fluid.
Only way you will find out for sure is to run a pressure check on the system or have a shop do it. Bear in mind that if a shop does the repair, they will either want to replace the unit with remanufactored unit (most likely) or rebuild this one (less likely). Either one will run you upwards of $1,000 or more.
As for the pump failure, if that's the case, there is a gearset that can be purchused from Sonnax that can repair a pump assy. A little more info can be found
here. You may also need a seal kit as well, but... at this point, you might be better off looking through the CD4E FAQ's and finding BT's rebuild thread. this will give you an idea of what your look at getting yourself into.
Best of luck and if there are any other questions, fell free to ask!
