Yep change your plugs to deans. just cut off the old wires one at a time so you don't short the battery and solder on the deans. make sure you connect them right so you don't run it to problems when trying to charge it. when you charge your lipo's plug in both plugs not just the small one with 3 wires
i'm not sure your problem with keeping it straight is the tires. the person you got it from might have it set up for (CS)/counter steer or could just need some toe adjustment but new tires are easy to make and easier to buy.