I am from the "if it's not broken don't fix it school". I would put the brakes in and drive it around and see. I would for sure drain the diff oil and refill it. It is a good possibility it was mistakenly overfilled and caused the seepage. The car must be on the ground with the axle tubes level when filling or the tubes will fill up and when they level out it will be overfull. I also get them level when draining the diff. Also many times a leaking seal will stop leaking if you drive it around after sitting for a period of time.
The bearing and seal change is a straight forward job. But it requires a long jawed puller to get the bearings off. I just made one with long pieces of angle iron drilled and put on my puller. Also when putting the new bearings on I put the axles in the freezer a heated the bearings with a blow dryer. They fell right on and when everything stabilized they were on tight. I also put Loctite stud and bearing mount on the bearing to axle contact area. The nut holding the bearing on needs a special spanner also, my snowmobile shock adjusting wrench fit perfect, but you could use a punch if you don't mind dicking up the nut.
Fix the brakes fill the diff and drive it, that is my advice.
