You have a broken screen. You don't seem to be able to 'restore' the operating system given all the great advice here. Especially calling Apple. I doubt they will charge you to walk you through the steps; but if they do...go for it.
Likely no end user will buy your laptop with a broken screen. Sell it as is and just move on.
Go to Apple's Trade In website to see what it would be worth in different conditions...you will need the serial #
https://www.apple.com/shop/trade-in
Best of luck

While I was getting my computer ready for sale, it slipped off my lap and hit the wood floor damaging the screen. The result is banding on the side and bottom leaving the screen about 30 % unusable. But wait, it gets better. Then I was removing all personal data from the screen and wiped out the operating system by accident. I looked at DIY information for restoring the operating system but I couldn't get it to work.
My plan is to sell the computer as salvage but I would like to restore the operating system first if possible.
Can anyone help with simple instructions?

The nearest Apple store is about 170 miles away.

PS- this is what I have done:
I turned the computer on and tried the recommended combination of keys to start the process without results
I researched U-tube videos but the ones that might have been helpful were of poor audio and video quality making it very difficult to follow
I took it to Best Buy but mostly what they wanted to do was sell me their 200.00 maintenance plan and estimated $400-500 to repair it when all I wanted was them to re install the operating system- not replace the screen.

Thanks everyone for your help!!

The reason I want to restore the operating system is to get a better salvage price. The cost new was around 1800.00 and I'd like to get some of that back. It is a 15 inch computer that looks good and worked fine. Without the OS I don't have access to the computer specs that a potential buyer might want to know. It's about 6 years old with a SS drive.

To the person that wondered how I managed to erase the OS - valid question. I hit the wrong choice when I was removing the data. It was an Oh sh_ t moment seconds later but by then too late. I know what I know for photography purposes but my general computer skills are basic.