No. As I have already said, if a weapon has stagger lock it will not lose it. Weapons evolve through a transformation catalyst. If you notice once a weapon is "stared" only it's relavent catalyst will be "clickable." Use it and it will change into the next weapon.
Here's a list of weapons with their catalysts.
Final Fantasy XIII Weapons

Catalysts are expensive but you can find most through the game, just traps are rare and insanely expensive.

EDT: Or if you want guides go to GameFAQ
Final Fantasy XIII FAQs, Walkthroughs, and Guides for PlayStation 3 - GameFAQs