Absolutely. All RW 1.0/2.0 phones are eligible for reactivation, (excluding the beta DefyXT and Optimus devices).
[edit: Have you tried any troubleshooting steps?..this one has proven to solve some issues… Clearing the Cache ]
The SIM card question is irrelevant as there is no SIM in the G1 (in CDMA phones the SIM card is only used for 4G, which the G1 is not capable of accessing). For models that do support 4G the sim is tied to the phone, not the service, so that would require RW to send you one if you chose a different iteration of the G series and the previous owner removed it. (Moto G 1st/3rd Gen.).
All 2.0 phones on RW have to have the RW custom ROM built in, in order to be activated though…meaning it must be an RW branded phone.
Used RW 2.0 devices can be found on sites like Swappa.com, Ebay, and sometimes on Amazon thru 3rd party sellers.
See: Buying and Selling Used Republic Wireless Phones
Reactivating My Republic Phone
Hope this helps.