I recently replaced my front brakes, since then everything seems fine, but just reading the service manual, it mentions shims that should be cleaned and put back in... these were not in the calipers when i did the change.. which I presume means the previous owner neglected to put it... like they did with half the bolts and screws in the bodykit...

Now, what are the shims for? am I going to brake for a kangaroo one day and end up annihilating the car when it fails to stop or will I be fine?

Pretty sure they are an anti-rattle device..
You will be 100% safe without them buddy. If you are still wanting them, pick a set up at the wreckers :)

my car hasnt had them on the passenger side for 100,000k's and its fine, brakes dont chatter and they still wear evenly.

For memory they may be an anti rattle/squeal device.

Most people throw them out with the first pad change.

Your car is fine without them buddy.

Ah nice relief :) cheers guys