Installing a fridge slide on top of an existing drawer system should not be too difficult. With most drawers, the deck lid is made from wood. The Fridge slide will have mounting tabs that will act as a guide to drill holes in your deck lid. You can find installation instructions in the "install" tab below the product photos in the link below.
https://www.frontrunneroutfitters.com/en/za/front-runner-universal-fridge-slide-for-40l-to-52l-fridges.html The interior dimensions of the 40L-52L fridge (FSLI005) slide are 736mm / 29" L x 469mm/ 18.5" W. From previous experience your fridge does fit. But please make sure to measure before making the purchase.
Front Runner team.