I've only had a couple of cartridge bearing hubs where the bearing was removable by hand...Phil rears. All the other required a little persuasion. They aren't a super tight fit but they still need to be driven out and pressed back in.

To get them out, spectastic, you may need this tool and a drift punch. They don't need a lot of pounding to get out. Once out, the replacements are pressed back into place with with socket or with fender washers on all-thread.

Check with the manufacturer, however. There are usually procedures to remove and replace the cartridge bearings. Phil Wood, for example, uses the axle to remove the bearings. It's not difficult but it is a little elaborate. Others have other procedures.