I used to help as crew at some of their races. My favourite was an Aston Martin DB5 they had that was bright orange with white go-faster stripes. A pretty heinous thing to do to an Aston, but it still looked great.
It depends on the day really, I work with a lot of prototype vehicles which means a lot of the parts are new designs and it could be the first time they are used. This means that things can go wrong but not all the time!
A lot of my job is about problem solving and developing an understanding about exactly how new parts or new software is working then making sure that any problems we do find do not happen again. Sometimes this means working on the car, sometimes in a laboratory and sometimes on a computer.