3-speed manual leaking fluid

I have a slow but steady drip of fluid from my 71 Duster's 3 speed manual transmission. the drip is coming from the rear of the transmission where the drive shaft/spline enters the transmission. I recently replaced my U-joints and I recall there being a good bit of vibration that probably stressed whaterver seal is in the rear of the transmission. My question is this: If I remove the spline - is there a seal that I can get to and replace without tearing into the transmission - or am I looking at a tougher repair?

Second question: What kind of fluid it recommended for this transmission.

tx,
Ken