As you've noted a slick all glass phone comes with a price.
Pop into an Optus store to discus repair options (I hope you're not leasing the phone?).
But otherwise I'd suggest you just visit a local shopping centre or google phone repairs in your area to find one that can fix it.
Are you leasing your phone? If so then technically you need to get the phone fixed by Optus.
Otherwise you own the phone and your free to get it repaired by anyone. A mobile repair store will likely do it in 15 minutes. Send it on to Optus and it might be 15 days
I presume you don't have insurance otherwise you'd have made a claim already. As far as an Optus store is concerned, they don't have the ability to quote you a price for the repair on the spot. The handset would need to be sent to our warehouse for assessment. We'd then contact you with a quote and ask if you'd like to go through with the repair.
The average turnaround time is 5-7 working (however this can vary).