Replace the flux capacitor with a brand new one. It's like getting a new phone, but with more explosions.
Estimated time: 5 minutes
Cost: 1000 Galactic Credits
Try to jury-rig a replacement with some duct tape, some twine, and a can of spray paint. It's like fixing a broken toaster, but with more sparks.
Estimated time: 3 days
Cost: Free (you already have the duct tape)