92 735i - Transmission problems

I have an automatic 92 BMW 735i. I just bought it. The person I bought it from said that its been sitting for 2 years and the transmission "veins" are plugged with old tranny fluid. When I drive the car it doesnt want to move, will rev high, 4k rpms before it shifts to 2nd gear. Come to find out there is very little fluid in the transmission.
My dad is a mechanic but doesnt take apart transmissions, but today we drained the transmission seeing that less than 2 qt of fluid came out, but very clean and there was a new gasket and filter in it. The pan itself had a leak so we swapped out the pan with a different one. We refilled the fluid, about 4 qt and shifted the gears around then took it for a drive. The car actually wants to move now without even touching the pedal and feels like it wants to go but its still having trouble shifting into 2nd gear, will still rev high before shifting. We are puzzled to why this is not shifting. Could it just be the solenoids or can it be that the "veins" are really plugged, and if so what are the veins of the transmission?
Also it came with a spare transmission that use to be on the car before the previous owner swapped it out. He said that the plastic reverse pump went out thats why he swapped out transmissions. What is the plastic reverse pump and how hard is it to replace?
I just bought this car and there is going to be free smogs on saturday and I desperately need to get it running!!
Thanks

Try to clean all solenoids with acetone or smth else

When the previous owner dropped the transmission and put the used one in, they failed to disconnect the steel wire that goes from the throttle body to the tranmission. So they broke the plastic piece that adjusts it causing there to be too much slack, hence the car reving high before switching gears. I contacted the dealership and itll be $45 for the part so Im just going to pull one from pick n pull.