Would be nice to know wich format you are shooting to give an acurate help.
But up to 6x7 you should be fine with a 80mm from Nikon, Rodenstock or Schneider. And if you want the best for wide open take an APO.
Find a good camera repair mechanic and get it popped open and cleaned.
It's a common problem with enlarger lenses. If you are happy with this lens there's no need to buy another.
I think as gareth harper, if the fungus is not huge ther is no problem. If the fungus is too big the covering could be damaged but you need a great fungus to do it.
If the lens is realy dead replace it with another rodagon. I have several with no problems but then I live in a desert, we have trouble growing anything.
Had this problem once with both a Rodagon and a Schneider Componon-S. Sent them both to a good repairman and had them cleaned up. They are working fine again.
Then I bought a dehumidifier that sits just outside my darkroom door.
Good luck.