In short, yes! If you import the corrected form it will bring in all the numbers including the corrections, not just the corrections. So your hunch is right. If you want to use "import" for the corrected form you would want to delete the original form it's replacing.
Alternatively, like Monika mentions, you can just make individual corrections, as there is usually just one, or maybe one with a couple consequences, so two or three entries to correct. Do whichever you find easier.
Also, depending on your reporting party, the corrected form may not actually import, because they may not have posted the corrections through to the "portal." Of course, these days it seems like everything gets more automated.
