That is a go to site for pricing. I have bought a bunch of random replacement pieces from the site for reasonable prices. The only thing is to try to get a pretty big list together to buy for pieces since even minimum USPS shipping is over $5. You can buy a replacement piece for pennies, but then have to pay shipping. I haven't tried selling anything through bricklink. When I was pricing items based on past email sales, I would get several people that would state the price on bricklink is x, so that is what I use now to price my sets. Ebay and FB probably have a much wider audience, but bricklink might not be a bad second option. I'm not sure what it takes to set up a shop, or if they take a cut like ebay, but you may want to check them out.
If you aren't in any particular rush besides having a bunch of stuff taking up space in your house, I would play the long game. We do have high inflation at this point, so it may not be the best time to sell. I'm getting random hits on my stuff, but have only made two or three sales in the past few months. Just hang in there, and you can get the value out of it.