Not only is it okay to do a full boil, but your beer will actually be better for it. However, bigger boil volume = better hop utilization, so you'll squeeze more IBUs out of your hops. Your beer will be more bitter than the kit/recipe is designed to give you. You can adjust for that by scaling back your bittering hop amounts. If you don't have BeerSmith or similar brewing software to help you do this, just post the recipe and I'm sure somebody on here will run the numbers for you and help you out.
You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer. -Frank Zappa