Trackpad very sensitive after spill

Sounds like the touchpad is damaged. Here’s the guide to gain access to it: MacBook Pro 13" Touch Bar 2018 Trackpad Replacement

As this series is so new I don’t know if the older unit is the same or not.

• 13” MacBook Pro Touchpad - Space Grey, Apple P/N 821-01701
• 13” MacBook Pro Touchpad - Silver, Apple P/N 661-13160

You may also need a new cable as well.

Your only other option is to visit an Apple Store or Apple authorized service center letting them fix it. But I would do one thing before talking to anyone! Sign up for AppleCare+ if you haven’t yet! It should have in covering the costs as you get a discount for things like this.