$40 for that change IS a good deal. Did they call you and offer it to you or did you just decide to change? If you book a Guarantee cabin (which basically means you pay the lowest price for a category of cabin an then Carnival assigns a cabin that is available) then sometimes you can get a free upgrade to a better cabin. But if they call you and offer you an "upgrade" for a price, then its truly an up-sell call despite the fact they call it an upgrade... Regardless of how you got it, it is still a good deal. I would pay $40 to be on Lido versus Riviera wouldn't even have to think about it.
Hope you enjoy your cruise! 40 days will fly by. I remember when you first came on here asking about cruising and wanting help choosing one.. now its almost here....
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14, Freedom x 2 6/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013