brake pads are really easy to put in. you'd probably want to leave them in if you got the hps pads. they are good for street and track. they should be a lot better than your stock pads for both applications. but if they got noisy or something you could always put your stock pads back in.
well...they will probably stop working after a couple of laps. they aren't designed for the temp your brakes will get to when on the track.
i know this because i went to my first track event a couple of years ago with stock pads...and i was really disappointed to find out that after a couple of laps my brakes basically didn't work anymore. so i couldn't push my car nearly as hard as i wanted to...cause i knew it just wouldn't stop fast enough in the corners.
if you don't know how to change your pads...you can get a haynes manual or chiltons from autozone or any other parts store. it's super easy..it probably won't take you more than half an hour your first time.