Water spill, keyboard and track pad not working

You can replace the keyboard without doing the whole upper case however the original keyboard is riveted on making it fairly difficult. You need to rip the old keyboard out and take as many of the rivets with it as you can, then you can add screws where the rivets have been pulled out to fasten the new keyboard. If enough rivets don't come out with the old keyboard to properly secure the new one you will to manually remove more of the rivets so you can fit more screws.

Before you do the keyboard and trackpad you should check for corrosion on the logic board from the water as the issue may be due to damage on the board in addition to, or rather then either of the components.

If both the keyboard and the trackpad are out, one possibility is a damaged upper case cable. It's a ribbon cable that attaches the trackpad to the logic board. Since the keyboard connects to the trackpad through a separate cable, both systems can be affected by a damaged cable. The power button working makes this less likely, since that button runs through the same cable; but it's possible that some traces are shorted out while others still work. In any case, a cable is the cheapest and easiest thing to replace. If it works, great; if not, you haven't thrown a lot of time/effort/money at the fix.

I spilled about half a glass of water on my macbook air keyboard and immediately used a towel to dry the surface, i tried to use the laptop and the keyboard was working and when i moved my finger on the trackpad however when i tried to click something using the trackpad it wouldn't work then realising that it was probably broken i wrapped it in a towel and put it upside down (not realising that you had to turn the laptop off) 10 mins went by and i read websites saying you had to turn it off so i did and re-wrapped it in the towel what sould i do i really don't have the money to get it repaired or a new one help!

Me too ! how do you solve it ?

I had a similar problem. water was spilled on a MacBook Air (2015 I think), after drying for a few days, it turned back on, but the keyboard and trackpad were not working properly. They were working, just intermittently. I took the laptop apart, and removed the trackpad cable. There was a small amount of corrosion on one end of the connectors. Using some alcohol and a Qtip, I was able to clean it up. Reassembled and it works great!