Is there anything that you don't like about your mini? If so, change something that will make it work how you want it to. Otherwise, leave it alone and spend money on playing.
Spraying your mini will knacker it - you need to have it anodise, which chemically bonds the colour to the metal. Paint WILL flake off and look horrible, as well as most likely going on so thick as to prevet parts screwing together, or moving freely.....