You should check out DankPods if you're really into that sort of stuff, but from what I can tell from your interests in Apple tech, you've probably at one point already saw his videos.
Shuffles are basically the same story as a nano, except parts are somehow even more difficult to find since no one wants a usb stick with a headphone jack.
iPod Shuffles aren't really a lot of money if you look in the right places. I recall that they were £30 when they were sold in Argos, a store in the UK, before they got discontinued.
@Chary iPod Nanos suffered a lot from battery plague to the point that the battery would start to bloat up towards the screen, resulting in the infamous 'black spot'. In many severe cases, if this problem is not treated immediately, then it can lead to fires.
Yeah, I found it for $5 at a thrift store, but I left it, as cute as it was, I don't have the means to repair it/I didn't want to keep it in a jar forever ala dankpods lol
the issue is that most nanos have a soldering requirement, and id really suggest having a ton of experience with a small things before even trying to service a nano