As long as sprint will activate it under there service you would be able to do it. Call sprint tech support to make sure they can activate your esn number.
As far as unlocking it that is by far one of the easiest things to do.
Heres a link for nueSPL 2.47. Just make sure you download the unlocker which is version 2.47 and not the relocker which is version 2.07.
http://www.nuerom.com/BlogEngine/pag...HTC-Titan.aspx
I would backup your data before you unlock it... Its not supposed to reset anything but you never know...
Since your new a good program to backup your contacts, messages, appointments, etc is PIMbackup. I usually dont backup my messages because people say that it sends all your texts in the drafts folder when it restores it. Could be a mess..lol
Heres PIMbackup.
http://www.dotfred.net/