PC Supply -> Variable Power Supply + Function Generator

I have this old 400W power supply just taking space on my bookshelf. So I decided to turn it into a regulated variable power supply for my electronics projects. I am planning to use the 12V rails as a feed for a variable power supply utilizing the LM317, 1 5V rail for a (square/triangle/sine) function generator, and the rest of the 5V and 3V rails as additional power outs. I'm also planning to implant an LCD screen showing the supplied current, voltage of the variable supply, type and frequency of function generated.

Can this be done? Should I in some way (which I don't know of) insulate my logic and LCD circuit from the rest of the box? I need some leads on what parts I should start gathering and the course of the design.

thanks in advance,

I'd like to try this too...but my knowledge is not enough ....