I don't know about Net 10, but you need to bring its baseband to 06.15.00 (don't remember which tool), then jailbreak on 4.2.1 with redsn0w or similar and then unlock via Cydia with Ultrasn0w.
Upgrading the baseband might be already jailbreaking it, but can't remember.
Just notice 06.15.00 is iPad's baseband so you'll never be able to restore via iTunes, you will always need a custom firmware 4.2.1 (patched).