For as cheap as a tail shaft seal is & as little time it takes to change it...I would do that FIRST.
Over the many decades that I have been building cars, one of the sad things that I have learned is that cars that sit tend to leak. Drive them a little more & they tend to not leak as much. Example : Both my transport trucks have 2 quart larger capacity cast aluminum rear axle covers which raises the fluid level slightly. If one of them sit for more than 2 weeks, I have a spot of gear oil on the shop floor. The next time I drive it, no leaks for another 2 weeks. My 55 Nash Ambassador Custom Lemans didn't leak a drop of tranny fluid until it sat for a year, but now it does. Seals that are kept wet with fluid continue to stay swelled & don't leak unless they need replaced.
God Bless
Bill
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