Well, if you are running a rooted ROM, you certainly have write permission on the partition containing the recovery image.
You could probably use dd (I don't trust it), or if you were being thorough you could use the appropriate executables from CWM recovery (statically linked executables) to flash the recovery partition right from a (root) command line of the running ROM O/S
Obviously it should be the second to last thing you do - the last thing done would be manual removal of the Superuser kit (.apk, su binary, dalvik cache entry) from a root shell (terminal emulator). As soon as you exit that root shell, root will be forever gone & there is nothing left to do but a factory reset.
If you want to put tools (scripts or executable binaries) in /data/local/temp to assist in any of this, it's a good location as it is not in a -noexec mount, and will get nuked with the factory reset.
Note that none of this will relock your bootloader, and as soon as the device is powered up anybody can see that open padlock symbol.
But frankly I'm not sure why you would be worried about any of this, anyway - a damaged USB port is hardly a manufacturing defect that should be covered by a warranty return. I don't know why Google/Asus would be giving you a freebie on that... and if you are paying for a repair, what does it matter what is flashed onto the tab?