Yes.
If one of these upgrades is on a character, and I play another upgrade of that type to replace it, does the ability trigger?
[Source: WotC]
Yes. Replacing an upgrade this way causes the old upgrade to be scrapped.
The cards
Dismantling Claw,
Reactive Armor and Personal Targeting Drone say "When this upgrade is scrapped from a character...". Do these effects trigger when the character is KO'd and the upgrade goes to the scrap pile? Do these effects trigger when you replace the upgrade and it goes to the scrap pile?
[Source: WotC]
Yes and yes.