SC40V8

Hi i have a 1993 SC400 bought it a year ago and it was perfect, but not im having a trans problem. When i shift in to Drive it shift hard but after shifting into drive it shifts just fine in all other gears. I have a supra trans that came with the car from the original owner that had planed on supping it up but never got around to it. so now i have it and it has less then 25,000 mile so its still brand new and was gonna wait to install it when i got money to start adding performance parts to the car. so i have a couple questions>

1. can i fix the old trans and whats involve with that?
2. should i install the supra trans and if i do what do i need to install it?


1993 SC400 220,000mile and still running!!!!