Assuming that there wasn't a lot of lemonade and/or that it wasn't spilled directly onto the area of the wireless card,
Check to see if your computer can see ANY wireless networks at all. This can be done by either using another laptop to create an ad-hoc network. You should also try to connect to one that isn't visible by entering the SSID and Password manually.
If neither works, check to see if the driver for your adapter is working correctly.
Quick question: When you accidentally spilled Lemonade on it, did you keep the computer on? If not, you may have short-circuited the chip (which may also explain the reason why your trackpad is not functioning).
If it was a very small amount of lemonade, open the laptop and check to see whether the adapter is firmly connected to the connector (whether it be a chip-and-ribbon type or just a card).