what transmission will fit?

[lsmalley]

I need to know what transmission will fit my 1990 190E 2.6 automatic. What is my transmission number 722.4xx? It is the original. What do the last two numbers (xx) mean anyways? I have seen 722.3xx or 722.4xx but I don't know what that means. I have seen a few rebuilt transmissions, in particular a 1990 190E 2.6 (722.4xx) and also a 1990 300E (722.429 I think, or to be safe 722.4xx). Will a 300E transmission be a simple plug n play installation? If there are two different models, i.e., 300E and 190E both having a 722.4xx, are they interchangeable without doing anything weird other than bolting it on to the motor and calling it a day? Sorry for so many questions in post, just trying to make sure those that reply aren't confused and can answer accordingly.
Cheers!