I'm servicing a new-to-me old mtb that I will use as my winter commuter. I have never disassembled a bike before but am taking this one apart bit by bit as a learning experience. I've just removed the suspension fork and cleaned the all the headset pieces (forgive my lack of bike lingo). Now, it is advised to examine the condition of all these bits n pieces though I'm not exactly sure what I am looking for. I think the most important parts here are the bearings. I think they look ok, the bottom one (right) looks more worn than the top (left). I read that I can swap them though like swapping tires. Is this true? And do they look ok? What else should I be looking out for?