Changes Permitted says to me that you can make changes
Whether economy, business or 1st doesn't matter.
It also states in what you posted
Originally Posted by fare rules
WHEN CHANGE RESULTS IN LOWER FARE SUBTRACT RESIDUAL FROM THE PENALTY THEN ADD-COLLECT/REFUND - REFUND VIA VOUCHER
which shows that you would be elegible for a voucher
If not 100% sure, just phone expedia and ask