I recently replaced both of my rear wheel bearings and seals due to a leak that got all over the parking shoes. It turns out that the differential breather was clogged, so the differential vented through the axle oil seals.
While you can just replace the seals, if the oil has leaked through to your parking brake shoes, you are supposed to replace the bearings. This is because the oil will have washed the grease out of the bearings, and once you replace the seals, they will be without lubricant.
With the right tools, the job isn't too bad. You will need a 20+ ton hydraulic press (I used the one from Harbor Freight), a rear axle bearing tool (linked below).
FWIW, the hardest and most time-consuming part of the whole job was reassembling the parking brakes.
Also, if you want to save costs and get the exact same part as OEM, Koyo is the OEM supplier, and replacement bearings for these trucks can be had for around $200 for the pair. I am happy to list out all of the part numbers and tools needed if you would like.
Rear axle tool -
Rear Axle Bearing Puller for Toyota 4Runner 4th & 5 generation 2003 up | eBay