Hide a lightbox button?

Site URL: https://www.sunlighttax.com/moneybootcamp

I'm new to Squarespace since I just started a new job in January. We're currently selling a product on our website that uses a lightbox mode form that pops up to fill out when people buy it. 

I want to be able to hide or disable the form if we sell out of the product so that I don't have to rebuild the entire form once we want to sell it again later in the year. The button is at bottom of page and says "Yes, I want to get serious about my career (with taxes)." I would let people know that the product is sold out by replacing the picture that says DFY Bootcamp with one that has SOLD OUT added across the top. 

I've seen other posts that mention using CSS to hide the form; how would I do that? 

Thank you, BaNgan! This is a neat tool! The only issue that I just realized is that the buttons above on the "tax" side all lead to the bottom button that I want to hide. So I'd need to hide all of the blocks and can't just disable the buttons? We were hoping to put Sold Out on them so that people know they were available before. Maybe I could put pictures up that say sold out in the place of the other blocks? 

On 3/2/2021 at 8:15 PM, EileenCos said:

Thank you, BaNgan! This is a neat tool! The only issue that I just realized is that the buttons above on the "tax" side all lead to the bottom button that I want to hide. So I'd need to hide all of the blocks and can't just disable the buttons? We were hoping to put Sold Out on them so that people know they were available before. Maybe I could put pictures up that say sold out in the place of the other blocks? 

Great idea, i will look

@EileenCos I see on mobile, images is left-align. Do you want to center them?

and icons look big.