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You'll need to contact your Cellular Provider where you got the Dual Touch. They will be the ones to offer the upgrade.
On a separate note, HTC frequently provides updates directly to their users, but the ROM version they provide may not include a lot of the extras or necessities included with the tweaked ROM provided by your Cellular Provider. Use of the HTC ROM may in fact void your warranty through your Provider and potentially render your device useless.
The choice, however, is yours to make. Good luck in your future endeavor, regardless of your choice!