LGT(Leo's Games Tools)

It will not be easy, but I hope that there are tools for that.
The arenas just to rip some textures, hopefully in the near future it appears the tool to rip models including race tracks, as of course

There is an alternative if you want the cars and the tracks of d1 and d2, you can rip the modified version (Destruction Derby 2 Carmageddon 2 Total Conversion), and use the necessary tool.

Modded version and download: http://destructionderby.wikia.com/wiki/DD2C2TC
Tool for import tracks and cars: http://www.carmageddon.com/forum/topic/26916

 Or have patience to have the necessary tool.