The hatch was a christmas gift, but are affordable on the typical amazon/ebay. Screws weren't included, so I ran out to menards to get some flat ones.
First, i took a sharpie and drew a circle around the inner hatch circle, giving me a line to cut out. Then I used a drill to cut an initial hole in the boat. It was a hole big enough for step 3, the tiny hacksaw i used to cut around the line. After sawing for about 20 minutes, I punched out a hatch shaped hole. From there, I gorilla glued and screwed in the new hatch. The glue is to form a water tight seal around the hatch. Since the hatch is located on a cargo depression of the boat, I wanted to made sure water wouldn't pool/pour in. Basically, the screws anchor the hatch in, and the glue seals it. Gorilla glue expands, so it would fill in all gaps as it dried.
From there, I just had to scrape off the excess glue (once it's done drying/expanding), and we are done!
Easy project, took no more than an hour of labor, plus dry time.
Unfortunately, this was on my stolen kayak, but experience is worth something.