I would tell your mechanic that the rear axle seal has been redesigned by Toyota and it requires the retainer to be flipped in order to get a good seal.
If you're planning on doing it yourself budget twice as much time as you think you'll need lol Besides the normal tools, you'll need snap ring pliers, axle bearing/retainer puller/installer (there's a loaner tool here on the forum or you can buy one off ebay), bearing grease, a sharpie, brake fluid, and a flare nut wrench. I recommend getting these to plug the brake lines while they are loose so you don't use lose all your brake fluid: Amazon.com: 40 Pc 1/16" to 3/4" High Temp Silicone Rubber Tapered Plug Kit - Powder Coating Custom Painting Supplies: Automotive I found a 4" x 4" 1/2" thick piece of steel plate was helpful to put on the axle to press everything back together.Yeah that seems to be the best way to approach it without getting kicked out of the garage. I think I can do it, but then again a few posts earlier it was mentioned that it can go south quickly once your all in. My concern is when I say I think...
I recently went with larger wheels and tires and I want to regear the rearend. My mechanic said that since my T4R has 210K miles, he suggests replacing the rear axle's seals and bearings while he's already working on the rearend. Is replacing the seals and bearings too early for the miles it has? It's not leaking. How many miles does the rear axle go through before it starts to leak? All my driving has been on streets. No offroading.