1995 Chevy Astro 1995 astro noisy rear axle?

background THIRD astro w/ noisy rear axle. not a howl, BUT A slight drumming progressing, to a 'vibration at x-way speeds'. noticed a SLIGHT right axle seal leak. [ upcoming replacement of rear brakes. considering replacing the axle seal myself.]
IS THE AXLE SEAL AN 'IN-THE-DRIVEWAY' REPAIR?

[as this is not my first noisy chevy van axle..................]
IS THERE AN INHERENT PROBLEM w/ THESE AXLES?

ANY ADVICE REGARDING REPAIR PROCEEDURES???