You can put any SIM into any phone (provided the phone is not locked to a particular carrier) and the phone should work just fine.
If your SIM is not working, you will need a working SIM card, so you will have to get one from somewhere to replace the non-working SIM card.
Assuming your wife ports her account across, then she can use her SIM card, so no need to get a new one for the iPhone as your wife should be able to use hers.