For an old Motorola RAZR V3 -- simply swap the old RAZR SIM card into new 8830, turn back on BlackBerry, click on "set up wizard", you should see a line for "import contacts from SIM", DO IT!
[Loading, loading. Done.]
Turn off 8830.
Swap back in new SIM.
Fire it up -- wah-laa -- all the old RAZR contacts.
I couldn't find this FAQ on the Sprint or CNet sites. I figured it needed to be written.
(Note: Sprint advises against SIM swapping from rival carriers. Whatever.)