Packing and Tearing Apart Linear Bearings for Anything (Prusa i3 Mk3)

Curious what's inside a LM8UU bearing assembly? Ever wonder how to pack grease in those (or weren't aware you should)?

With the Prusa i3 Mk3 MMU2 unit removed I've decided to install the Mk3S modifications and install new properly grease packed bearings. I'm also taking off the IGUS RJ4JP-01-08 linear bushings that have been holding on the Z axis to see if they've worn.

Going through the process I noticed that the Z axis rods tolerances are a bit off. From what should be 8mm to around 7.85mm~7.95mm. Which does explain the noise from the rattly un-greased bearings that prompted the IGUS replacements in the first place. ... https://www.youtube.com/watch?v=Xzd492yc1ME