A blowoff tube is just a tube inserted into the mouth of your carboy that allows all the krausen that builds up (which there will be a lot of in a fruit beer) to escape. If you don't have one it will go through your airlock and onto your floor, that one I know from experience. I've had fruit beer made two different ways, I added whole crushed strawberrys to my primary (open fermentation in a plastic bucket with lid) which yielded a slight strawberry taste. I also had a raspberry wheat made by a friend of mine which was made by adding raspberry extract during bottling, this version had a much more powerful fruit smell than mine, and also a stronger fruit flavor in my eyes. Mine also got better with age. Either way you can do no wrong as long as you sanitize. You're already making your own beer so either way you're a winner.