The shields are nonremovable. Use a syringe to oil. Recommend using skateboard oil, sewing machine oil, or other low build high endurance oils. Keep away from plastics, or use plastic safe synthetics like super lube.

Remove the bearing from the TT base. Soak whole bearing in acetone, again the shields are nonremovable. An ultrasonic cleaner with acetone as the cleaning solution can help speed up the soaking process and improve cleaning. Recommended to do this the moment any drink has been spilled on the TT, like beer or soda. Relubricate the bearing after cleaning.

If the shields have been damaged, the bearing is seized or if even after lubrication the bearing is grindy and does not spin well (balls are pitted), replace the bearing.

The bearing on the underside (the side with the tt mounted cylinder with the c clip) has a retaining c clip mounted to it. Stick a small screwdriver underneath the retaining clip and pry it up.

Take this c clip off the old bearing if your new bearing did not come with one.

To put the new bearing in, you will find that the main thing holding the bearing in place is friction. This means that it's pretty hard to get a bearing back in there. I took a wood block and a dead blow mallet and knocked it back into place slowly until the retaining clip was flush with the bottom of the TT base.

So long as you get a 6805 size ball bearing from whatever manufacturer you should be fine. I would recommend against using rubber sealed bearings and flat outer ring bearings. For the former, they may be easier to service but they act as a friction point against the felt in the TT. For the latter, flat outer ring bearings are harder to align and harder to remove. However, bearings that have a retaining clip groove and flanged bearings should work equally well.