Personally, if the NAS is up and running, I'd migrate the home directory and anything else important from the desktop to that, and intend to network host those folders; set aside the 1TB, install the 2 TB, and do a fresh install and see if I can still get to everything happily.
Alternatively--if you want to preserve stuff locally--new drive in an enclosure, attach to desktop, boot from an install USB, fresh install to 2TB, reboot from 2TB, mount 1TB, migrate data, install 2TB. I don't think there should be a UUID problem doing that, but even if there was you could still boot from the install stick and try manually fix it
Personally, if the NAS is up and running, I'd migrate the home directory and anything else important from the desktop to that, and intend to network host those folders; set aside the 1TB, install the 2 TB, and do a fresh install and see if I can still get to everything happily.
Alternatively--if you want to preserve stuff locally--new drive in an enclosure, attach to desktop, boot from an install USB, fresh install to 2TB, reboot from 2TB, mount 1TB, migrate data, install 2TB. I don't think there should be a UUID problem doing that, but even if there was you could still boot from the install stick and try manually fix it