Diesel Bombers - Tranny questions?

Hey guys, I have a few questions about the tranny in my 92 dodge. Any advice would be greatly appreciated, ok so I changed the fluid in the tranny, and in my service manual it said to use dextron III ..so I did and it ran horrible, I drove it to the trans shop and he said i needed 2 use atf + 4....so I drain oil added new oil and now, I the trans feels a little sluggish and down on power..could I have ruined the tranny by driving it 2 the shop? Also when I put it into drive I get a little bang from drive shaft, what would cause this?...tranny was rebuilt at 125,000 truck now has 160,000m any advice would help, thanks again!!!