Am I able to claim a ticket with a confirmation number at the Redding station on Saturday?

Yes

I actually called, and they are open until about noon

I don't believe they're open where they sell tickets there on the weekend. To be sure you may want to call the 800 number.

I don't think you can pick it up on Saturday; I think the Greyhound window is only open Monday-Friday. The confirmation number will allow you to get it though.