As you thought the convertor should just slide out. Be sure to support the thing by the front snout (where it centers in crank), so that you are pulling straight.
The only thing that I have seen that screws with this is if the front pump bushing is stuck to the convertor and has spun in the pump causing a groove. Use two large pry bars, one from each side and have some one catch it as you work it out.
Bosch Master, ASE Master, L1
33 years MB technician