in that update you may have been using wad mannager and you deleted a wad saying system menu if so full brick!! no way out, no signal screen, wiimote just gets to turn on the wii and then wiimote turns off, only fix is to change motherboard of a second hand one(around $100), buy a new wii (+$200) or nintendo will fix free if under warrantty and no softmod is found if not under warranty its aroun $100 if they dont find softmod!!
good luck!! (you can always waste some time and try savemii but aint gona work you got no signal..right??)
well they may ask what happened just tell them you where running a original game with a update and it froze cause if you really deleted the system menu there a low chance that they will find somthing well im sure it delet preloader but not 100% sure if traces of bootmii would of remain, i have read in previous forums in GBAtemp that they sometimes just exchange the wii in other cases they have a full report that some softmod was installed and Ninty will not fix if this is found...i think your not gona lose much more then what you have, if it all goes wrong you could sell its parts lots of wii's have drive problems(aprox $80), bluetooth prob(aprox $50), and pepole like extra wii motes(apx $30) you could at least recover $150 if it all goes wrong!!