I don't think the making of an extract is really necessary. One problem I see with this is that you will be heating the fruit, which will set the pectin in the fruit and lead to a hazy beer. Making a wheat, however, you might not be concerned with this as you may be drinking the beer with the yeast.
What I would recommend is simply throwing the fruit, diced, into the fermenter. I've had difficultly separating my pureed fruit out of beers when doing this, but it is easier with whole pieces. I would recommend simply making it like this, but with the strawberries diced: http://www.homebrewtalk.com/f75/requiem-raspberry-56285/ You'll probably get a beautiful color in your finished product!
You might also think about freezing and thawing the fruit before. This breaks down the cell walls, potentially allowing for a better extraction of flavor. Make sure you let this age for a bit before bottling, as fruit will keep fermenting longer than the rest of the wort generally will.