corrosion problems (mac LC iii)

I have a old Macintosh lc iii, It has a little bit of a corrosion problem. The caps have leaked, should I soak the board in 99% alcohol or should I use verry fine sand paper to sand off the corrosion, and use clear nail polish to seal it? Please do respond quick, because I don't want it to get any worse or beyond repairable.