good one.

BBs are reasonably easy (depending on the type) but you need the right tools, which is largely crank brand dependent. I have a BB30 press fit on my MTB. I just took that to the shop as I don’t have the tools and the cost of the tools is more than it cost to swap them over.

But external cups are relatively easy now days. there are heaps of youtube videos on it. one side is left handed thread (cant remember which). but they are usually on fairly tight so you will be questioning whether you are in fact turning it the right way 🙂