When I got a sprinter from ACT, I had to do a blue slip.
They check the standard stuff like Exhaust, breaks, lights, tyres. Stuff like that. The sprinter I had had a large exhaust and was lowered, sports steering, everything else was stock.
I has to change a broken park light and some balding tyres and that was it. The lady at the RTA said that they do random database checks on cars to see it they are stolen, can take a couple of days but I didn't have to.
So like Rob said if your car is in fine working order and you know it aint stolen then you shouldn't have anything to worry about.