No, they're all sealed units. There was a change in dimensions when they went from cast to composite rotors, which may explain parts book breaks, but the old ones were units too.90 was the changeover to hub units. you can clean and repack the older style ones 84-89 i think. the newer 90+ are single unit pieces. find a new parts store if you have a 90+
As far as "just" take the old hub off... well let's just say you will want to have your 4lb hand sledge on hand. You'll need a 13mm 12-point socket to unscrew the bolts, and you'll want another one that you don't mind beating senseless with the hammer to push the old unit bearing out (unless you are junking the old bearings in which case you can simply beat on the wheel flange.) Don't beat on the heads of the bolts though because you'll never get the socket back on them if you do.