Nashbar has a carbon fork with canti/v brake bosses for $100. You can get a decent generic headset for $15. Same thing for the stem. Add another $10 for a pack of spacers so you can actually raise it up.

That puts you at under $150 if you can do the work yourself. If not, I bet a shop would charge $75-$100 to do it, even though it's super easy to do.

Then you're out $225, with questionable ride quality, a big unknown for fit and handling, all on a bike that's probably worth about $300.