If money's tight I'd recommend the Epson V500 photo scanner. Although the productivity is significantly slower than a dedicated film scanner the results are surprisingly good. These scanners can be bought for about $150, or less if you check around. A decent scanning software would be 'Vuescan'. It works a lot better than that which came with the machine.
If fungus is gobbling up the surface of the slide I don't think there is any magic formula or process to halt or reverse the damage. You could scan the slides then manipulate them in PhotoShop or similar program, but this could be a tedious task to say the least.
Good luck.