Halving Durations of an Entire piece?

Hello,
I'm in a ukulele group and our leader has started trying to make lead sheets for some of the songs we do. She sent me one yesterday where she'd written what should be 8th notes as quarter notes, etc. Is there any way, in MuseScore, to fix this across the entire piece, without having to rewrite the whole thing? Since I don't want to run into copyright issues with the actual song, I'm attaching a verse of Jingle Bells, the first half where I've done what she did, the second half written correctly.