I did it. It was pretty easy. In fact, if you go to http://www.fixedgeargallery.com/wheels/ and scroll to the third method.
To sum up....

1. remove old freewheel.
2. respace the hub.
3. I think the link says something to the effect of loosen all of the drive side spokes half turn then tighten non-driveside half turn. Continue doing this until the wheel is about center. However...Too much dishing with a wheel that was intended for 6/7speed and you could end up with spokes poking through your rim strip tape and puncturing your tubes. Mine are as centered as they are going to be and i'm totally fine with it. If you are a perfectionist, you might need to get yourself some shorter spokes for the non-drive side.