Well, it's a sad state of affairs, but if you have personal data on your broken 8703e that MUST NOT be compromised, I think your only safe option is to take a sledgehammer to it and eat the cost. Do you really trust Verizon to properly wipe it, no matter how much they may assure you they will?

You may also try to insist they send the same unit back to you after repair (write down the ESN before you send it out). However I doubt they would commit to this, it is simply not their normal workflow.

I'll admit that this is speculation, but I highly doubt Verizon or RIM will attempt repair of your broken unit if it is a hardware failure. It is simply not cost effective to repair most consumer electronics these days.