It was sitting on my couch, fell three feet onto the hardwood floor, and now has a cracked cover and the lcd is "splashed" full of color so I can't read it anymore...it was bought in January of this year...

There are used/broken 880s on Fleabay and I thought I could buy it for cheap and then replace the lcd and screen myself but is the 880 the same as the 890 as far as the screen goes?

Yes they would have the same screen. Before you do that I would recommend calling Harmony Support though. They are usually pretty good about helping out with problems like this.