Yeah the new generation just doesn't have any small access panels just remove the whole bottom cover.

This guide refers to the 53-generation Nitro 5 (AN515-53) but I believe you are referring to the 54-generation (AN515-54). While they do not look exactly the same under the cover, they are very similar and the hardware is close to the same place and the RAM is installed using the same process.

You can purchase replacement trackpads online, on eBay or Amazon or many other places by simply Google searching “Acer Nitro 5 Touchpad Part”