If I had e-filed my taxes early, and had already received my tax refund, am I still eligible for the COVID19 stimulus package?

The details are still being worked out by Congress at this time. Once things are finalized we will be able to provide more guidance. You can also stay updated by continuously checking the following links. 

https://turbotax.intuit.com/coronavirus/

https://ttlc.intuit.com/community/tax-topics/help/how-are-my-taxes-affected-by-covid-19/00/1330402

https://www.irs.gov/coronavirus

yes 

the rebate has nothing to do with whether you owed or received a refund.