The folks here are a fantastic resource, but for a 1980's era C25, also check out the Catalina Owners site (Catalina - Capri - 25s International Association
). The folks there are great - I had a C25 up until this past October and learned a lot from them.
I was just looking into flooring for my "next" boat, and many of the manufacturers of flooring (unless you're going with solid wood) say not to use their floors in a marine environment. Your cabin will have high humidity levels, and be subject to significant temperature swings (in the NJ area, where I am, we see temps from about 100F down to about 10F, and most flooring is designed for temps in the 50's to the mid 80's, i.e. "room temperature"). The glues they use in the manufacturing processes just can't handle that much humidity and those temperature changes. The C25's interior isn't very big. Defender sells rolls of faux teak and holly sole. It's relatively expensive ($32/linear foot, 6' wide), but you won't have to worry about sunlight fading it, or water ruining it.