Bearings are commodity items. So measuring a bearing for ID, OD, and height/thickness and going a search will get you a replacement. Sometimes you might get an obsolete bearing configuration or size, but that's rare and generally only happens when working on very old or very odd equipment.

How easy are they to replace depends and you only get to find out when you go to replace said bearing the first time. This fan doesn't look too hard though. The photo shows a plastic bearing block screwed to the fan body and holding the bearing and motor in position. I would certainly investigate further. Other equipment can present other problems that you need to take into account. A welded bearing housing would be a repair nightmare.