Hi
It shouldn't be a problem.
For the import of the images, it would be best to directly upload them via FTP to the upload folder where they are stored in images/com_hikashop/upload/
That way, in the CSV, you can just enter the file name in the "images" column and they will be linked during the import.
If you have the URL of the image in the images column, then HikaShop will have to download the images for each product, and it will considerably slow down the process and since HikaShop will be limited by the "max execution time" setting of your php.ini it can potentially crash in the middle of the import if it takes too much time (no worries though, you can just run again the import and it won't break anything... it's just that not everything will be imported).
Regarding the update, it should not be a problem either.
1000 products is not much for the import process. The only issue I can see is the image downloads as I explained above.