Have a 70 Coupe Deville with a rear end leak. It appears to be from the front seal where the u-joint is. Is this replaceable externally or does it all have to come off?

Also, if it all has to come off, that isn't in my budget now to have done(I'm getting too old to do it in the driveway with just jackstands) can anything be done to help the seal for now? Thinking of some type of seal helper that those autopart stores sell to fix leaking seals.

Jeff