You don't even need to look at it. Side to side or radial play will tell you if it is worn. Also bad bearings will whine. Even if you inspect it you may confuse castor varnish with rust. The cage can even be rusty but the balls and race be fine. But if you are doing this as a learning experiance, then the cost is cheap education.
Also - pulling the piston out of the liner will not need a new break-in period. The piston goes back in the same way it came out - Since its going back into its same position, nothing will have changed.
Even if the sleeve is pinned it is very unlikely you will get this exactly in place, it may be microscopic but still out of place. Not to mention the risk of breaking or loseing something every time you take it apart. But I recall I took several engine apart for the education when I first started. You will most likely not notice the effect, especially with an ABC or ABN engine. This is more of a problem with ringed engines.