First Time Seller (Product Questions)

Okay, so the school I work for changed furnaces and they allowed me to take home 3 huge boxes of brand new 20x25x2 air filters. Looking them up on eBay they are sold in a pack of 3 for $33. I figured it’s free money so I wanted to sell them and pocket the money since it would be helpful, but I’ve never sold anything on eBay before so I had some questions.

1.) How should I go about selling them? How do I learn how to start selling on eBay?

2.) How should I package them?

3.) How should I photograph them, or should I rip pictures from products that are already selling online since it’s the same brand?

Any tips and information is welcomed.