You really have to remove the valance to do it.
First I removed the the phillips screw from each side at the bottom from the wall leaving the bracket still attached to the valance. Remove the round Ďbuttoní that holds the shade cord.
Then there are two screws up top behind the shade (bi&ch to get to!). Once these are removed, the valance comes right down with the shade still attached to it.
Then just remove broken shade from valance and attach the new one to the valance and reinstall valance.
Lastly is attaching the new buttons where the old ones were.
Sorry for the bad pics