Gus90, Try out Dashware, now that they are owned by GoPro the latest version of Dashware is available for free. It has much better syncing capabilities than Virb Edit. Also make sure, at least on your PC, that your video codecs are up to date. Two of the easier codec packs to install are Shark007 and CCCP Codec pack (google them). With Dashware as long as the .mp4 files are on your PC you can import them as audio tracks.

With respect to the 4GB limit, unless you are making a feature film, cut down the video. With all due respect, no one but you and any loved ones you force to watch them, will want to watch a 27 minute + video of your ride. Break it out to the highlights, then make a second pass and only select highlights of the highlights. Remember human attention spans are so short that advertisements are only 15-30 seconds long.