My friend accidentally spilled water on the keyboard of my laptop and I immediately turned it off and sat it under the SUN. It's been 3 days since that happened and I never turned it on ever since. I went to a technician recently and he said that it should be fix immediately. Do I really need to get it fix or I should just tell them to open the inside of the laptop and see if there's still moisture and clean it? Hoping you REMOVED the battery from laptop as well. The battery is what will cause damage as it sits WET. The battery still applies power to some circuitry and so if that circuitry got wet wet electronics that have electrical potential eat away metal through electrolysis. Placing the laptop into a large sealed bag with dry rice is one way to dry it out, but only seen this done with cell phones. Most laptops that took a bath survival of them is dependent on how much liquid, where the liquid exposure and how FAST electrical potential is removed from circuitry, as well as how quickly the electronics are dried.

If the laptop was left in direct sunlight and very hot to the touch for 3 days then it might be OK to apply power and see if it boots
The bagged rice trick works great for laptops as well.....course you need a zip bag large enuff...and more rice.I turned on  my laptop last night to see if it will boot and it did. Does it mean that its now okay to use it or maybe I should open the inside and clean it before using? id leave it be and not open it. Id run some testing on it, games , web surfing etc. If all works then you got VERY LUCKY  DaveLembke is right.

If it works at all it is dry.