Hello Crib,
in general there are dampening pads glued to the brake pads. So this might cause the stuck. Remove the cap of the brake fluid reservoir first. Push the old pads back as far that you can. Than you should be able to get them out. Don't use copper paste for the back of the brake pads; only for the duct of the brake pads (hope duct is the right word here). The Brembo brake system is designed for the dampening pads which pulls the brake pads away from the rotors.
Don't break the brake lines loose. You can change the brake discs without doing that. Just hang the brake calipers on a piece of wire, so that the brake lines aren't stretched.
Regards from Germany
Markus
PS: be careful. Brakes are important. If you don't know 100% what you are doing let somebody else with experience check you work.
Safety always first.