building up a car

[vectorspecialist]

i'm trying to get into scca racing. i have to do the licensing, but i have one big problem.
first, is it better to use a brand new car off a showroom floor, or is it better to go with used?
another thing, if i took for example a 98 honda civic 2dr coupe and wanted to race, wat would i have to do to make it leagle? and wat could i do to make it competiative? and wat other cars would b in its class?
thanxs