Simple Questions About Upgrades

OK I plan to buy/farm an Icy Dragon Sword, then upgrade it. My first question is: can these swords be upgraded? Secondly, if I upgrade it with a +28hp mod, can I later put on a +30hp mod and overwrite the +28? Also could i put a different type of upgrade to overwrite my previous upgrade?

Thanks

Yes to all of those questions

you can put any pomel on... you just cant upgrade the hilt of the IDS

really? oh dam it I though tyou would be able to