marine Jensen radio not work need help

Last fall I acidently reversed the polatity on hooking up the battery to our pontoon. The marine Jensen radio apparently was the only item that did not work afterwards.
1Q. Is this a major cost wise fix, would it be better/cheeper to just buy a new radio?
2Q. If I was to buy a Diode for future stupity, what size to buy?
thanks all.
That's what is known as letting the smoke out of the box. AFAIK, it's toast. (no pun intended).

Did someone say "toast" ?? Kitty had a bad day with one of those!
 

You wouldn't want to elaborate? 

I agree with the other techs on this one. There is no way you can salvage that head unit. Time to replace.