Great idea, Scaredgirl. (: I definitely think more quests would be beneficial. If I remember correctly, there's nothing that really covers the False Gods, PVP, Oracle, or HalfBloods.
However, I agree with Bloodshadow. The quests are basically tutorials, and we already have an upgraded card tutorial. Maybe I'm just sleepy, but it just seems to clash. Would this quest go before or after the Upgrade a Card quest?
If it goes before, it just seems strange. "Here's a free upgraded card, now go start working on another one." There's no longer any real excitement in upgrading a card on your own -- you've already got an upped card, why be forced to work for another one, already? As it stands, there's a reason to work for that upgraded card. It's cool, new, exciting. But if you've already got one, maybe you want to spend that hard-earned 1500 electrum on reconstructing your deck? I know I didn't mess with upgraded cards for quite some time after earning my first one.
I guess it would be alright if it went after the already existing quest, but I think a 1500 electrum prize would be better in this instance. Now they're aware of how to use the upgrading function, and they can choose what they want to spend the money on. Plus, you won't need to code a new window for the prize.
This leads me to another question; would the random cards be taken from the user's deck, or from the entire card pool? I'm assuming it would be from the user's deck, because taking 12 random cards from the entire card pool would be insanely unfair. If it's from the user's deck, again, it just seems strange. Why not let the user choose which card he wants to upgrade, by just handing him the 1500 electrum and giving him the full range of options? I think that would be the easier (and more viable) solution.