if you are successfully loading the TFTP images, then the WXL should be on the way to being able to update/reload a full firmware.
the yellow/amber flashing interval after loading the TFTP image should be on the order of about 20mins. sometimes, for whatever reason, my WXL would enter a state where the amber flashing would continue indefinitely. i let it go all night once, just to see if it was stuck or just slow. "stuck" seems to be the answer.
no matter, after a reasonable wait (like i said, 20 mins or so), turn the WXL off and turn it back on again. it should blue flash for a bit and then go to a steady blue. at that point it's ready to be reloaded via LS Updater.
have you edited your lsupdater.ini file by any chance? you should. there's a sticky posting in this Forum all about that. i recommend Force Update, Rebuild partition table and Delete user-config with your new disks.