Exactly. SoU is meant to be played with a fresh new character.
If you feel like me and are attached to your old NWN chara, save him and use him for HotU later (as his level will be somewhat appropriate there). But for SoU, the only tractable way to play is making a new character.
(ok, this method has the disadvantage that SoU and HotU are one unit story-wise, so actually the game assumes that you play HotU with your SoU character - but it isn't much of a bother.

)
-Zel