With most Gateway laptops, you go to the Gateway site, enter your serial number, go to support, and look for the online manual that has visual instructions on diassembling the computer.
All laptops are a series of screws, then snaps, and fittings. The most important tool is taking care to think about how it is assembled, then using some small amounts of silicon spray and powdered lubricants.
There are low cost plastic tools on eBay and elsewhere for splitting the case or plastic parts without damaging the computer,
Using small amounts of heavy duty silicon spray or liquid wrench powdered lubricant helps.
Removing the keyboard comes first. The rest comes more easily.
If it is a decent brand, there will be an online handbook that has drawings to show how and where and what.
On older computers, the plastics become more brittle as they age. Replacing parts that you have broken is just about impossible.