I don't know much about Privateer Remake so I can't help you but I believe this has been discussed before. If you run a search in the forums for it you might find what you're looking for. Or just wait for one of the guys who knows the answer to respond.
to change ships, go to the ship buy menu, then click on the ship you want and hit "buy" if it's at a different place it'll cost some money to hire someone to bring it.
You can get flyable versions from Perry Naval Base (when they're in stock!) after you finish the Steltek mission. To load up a Paradigm as a carrier, you can purchase the craft from Perry's market exchange. Read the manual for more info on ejecting craft to act as wingmen.