300td wagon needs transmission help.

[mercedes 300td]

Hello it has been a while. how is everyone doing.?
Well I have a chance to buy another wagon. This one a 1982 300td wagon. The problem is this one needs transmission work ( according to the current owner). My question is .two parts How much does the typical transmission overhaul cost on the 3 speed automatic in this wagon. ? Next. Will the transmission from my 1976 300d be a direct swap?
About 20 years ago I looked over the shoulder of a guy while he rebuilt the tranny in my old ford bronco. It did not look to be that difficult. Any DIY folks out there have any commments on a DIY transmission overhaul on the benz?
I do not have many details on this new wagon yet other than the price is going to be negotiable and under $1000
As always any help would be appreciated
thanks
mercedes 300td