So you're setting up a TSL patcher to install your mod using ChangeEdit, correct?
You wouldn't need to replace anything. Basically, extract the unaltered .2da from KotOR Tool to a place of your choosing. Once that's done, (I assume your using the compare two .2da's function of change edit) select the compare function and then when it asks for the Original, unaltered .2da choose the one you extracted from KotOR Tool. When it asks for the new, modified .2da choose the one from the mod.
If all else fails I should be able to set up a TSL patcher install for you. What mod is it?