I made two fixes to my 1987 Seiko 6309-729A dive watch, which I bought refurbished over eBay from the Philippines maybe 5 years ago.
I needed a ball bearing to make the click wheel click (and now I have 499 spares in case I lose one when removing the bezel).
The critical fix was to the minute hand, which was loose. Via YouTube videos, I figured out how to remove the crown, take the movement out of the case and push down the hand so it stuck on the spindle.
Can't believe it worked.
The watch cost me about $80. I wanted a Seiko mechanical dive watch, and this was the cheapest way to do it.