How to make a tunning car like need for speed underground

Hi every body im iniciatizing at ogre3d, Qt4 and ofusion i have a program based on QTOGRE, i create a class that update the mesh while i changed it from a database, i make some vehicles at 3dmax and create parts like wheels, hood, and spoilers, but i really want to make an update just over a part of the vehicle like in the videogame need for speed, i thought something like read the .osm file relative object space and overwrite that posicition with the another object but my programming level dont let me get there. any ideas please! i apreciated so much! sorry about my english