You already have the battery, so just use it. It will be a little harder on your gun then a lower voltage battery is, simply because it will cause your motor to turn faster, and provide higher amps faster through the trigger, causing it to arm a bit more. The faster things move, the higher the risk of them breaking.
But if you like the rate of fire it is giving you, then use it. The gun will break eventually, no way around it, may as well use it the way you want until it does. Then just get it fixed.
The one thing that is MANDATORY for using Lipo's is make sure you use a LIPO charger, and charge it using the small connector with 4 wires on it. DO NOT CHARGE IT USING THE DEANS PLUG.
Second, and highly recommended, is to use a lipo voltage monitor. This plugs into the charging cable while your using your gun, and monitors the voltage of each cell in the battery. If the voltage drops below a certain point, it will beep at you. The reason this is important, is because if you discharge a lipo battery too far, it will actually damage the battery. I would worry too much about getting one of these before your next game, because it's not very likely that you'll discharge your battery all the way in just a small game, just make sure you fully charge it before the game starts. (these are currently out of stock on this link, but just to give you an idea:
http://www.eliteairsoftbatteries.com/products/150-airsoft-lvc-for-3s-111v-lipo-packs.aspx)