Two hours is the cutoff for "significant" schedule changes, so they will be willing to waive change fees and refares for "reasonable" requests. IME, "reasonable" has some grey area, and can include routing, nearby airport changes, and minor date changes (e.g., I've added an overnight en route) to make the ticket work for you. I believe they'll also refund without the cancellation fee, but I'm not sure you'll get the vouchers back.

You should dig around and find the united metal routing that works for you. Then call. Just don't accept the schedule change until you're happy with your rebooking.