Upgrade System Software
The Sytem Software you want to use will depend on the amount of RAM installed. If you have 64MB or less I do not suggest OS 9x. OS 8.1 or even 8.5/6 will run better with less RAM than OS 9.1 from my experiences.

Painting your upgraded LC580
The LC case is aesy to take apart. Most of the case is in 2 pieces, the front and the big back part. This makes it easy to paint. Just remove the 5 screws holding the back on. Slide the back off , sand, clean, and paint it. I then taped off the internal parts and the screen for painting the front plastic. Removing the front plactic looked like a real pain so I improvised. I used Matte black because it works better on textured surfaces like computers. If you use a gloss enamel be careful to to get runs and overspray. Matte finish eliminates almost all room for error.