If you already have an unexpired State of California EMT card then you're good to go. California only requires that you obtain NREMT certification to initially certify. You can let your NREMT lapse so long as you maintain your California EMT card. To recertify your California EMT certification, you need to do 24 hours of CEs and a skills test.
Unless you plan on working in a state other than California or for some ungodly reason your employer is requiring that you maintain your NREMT...then you don't have to renew your NREMT, only your California EMT.
Edit: Just saw that your state card expired too.
So you need to do 48 hours of CEs....I would do a 24 hour refresher class plus 24 additional CEs. Additionally you need to have a skills exams (which will hopefully be included with the refresher course), and after all that, you have to take the NREMT written exam again. Good luck.