Is it possible to form a 501c3 non-profit for the purpose of a single event? Ie, to put on a single fundraising event (ie a theatre production which takes place over 8 performances with an opening night silent auction/raffle) where donations can be accepted to cover overhead expenses while the net profits are donated to charity; with donors receiving tax credit for their donation?

Forming a 501c(3) is a major undertaking for just one event. Wouldn't it be easier to find an existing organiation and run this fundraising through their organization?

Agreed. 501c(3) setups can cost a bundle to do properly.

THanks to both!
I am trying to find one that's set up already. Another option someone brought up to me is the Charitable Gift Fund though I don't know if there's any way to repay my overhead costs out of something like that or not...

I recommend you get a professional to run this project for you. There are too many pitfalls for an amateur.