Sprint TP2 - ? about using 3rd party SIM card internationally

[gloamer]

Some simple questions -- I know this ground has been covered here but I've read some conflicting answers and Sprint's info is not exactly forthcoming. So I just want to be clear...

I have a Spring HTC TP2 on the SERO plan. I'm heading to France in a couple weeks and would like to buy a prepaid SIM card while there and use it. What _exactly_ do I need to do?

- can I use a non-Sprint SIM card? Sprint obviously wants customers to use its international calling service for $1.29 a minute. Will the phone work with another carrier's SIM card?

- do I need to call sprint to unlock the SIM card slot or anything like that beforehand?

- Anything else I need to know? I'd like to avoid a surprise when I am there and have some confidence the phone is going to work after merely popping in the SIM card.

Thanks, appreciate the help.