It's up to you, really. You'll want to cover your cost in parts ($10 or so for the calculator is doable if you find someone with a broken one like I did.....you might be able to check your local high school and see if their math department has a TI-83 graveyard of some kind), then decide how much your time and effort are worth. I'm sure there are people out there willing to pay nicely for a mod like this.

By the way, I'd love to see a picture of your completed work. I hope you were able to do a nicer job on the backpiece than I did!