LG actually makes it very easy to reflash a phone. There are two programs, LG Mobile Support Tool and LG Flash Tool, each one taking a different file format of the ROM you want to flash. But you need to find the tool and the appropriate file for the phone, version of Android and tool, you have. It might take someone who's done it before a whole 5 minutes. (Everything takes longer the first time.)
Just find a kdz (or other format ROM) file, then download the appropriate tool and flash away.