help please

hi i just recently bought an 04 a4 with the 1.8t quattro, and the tiptronic. i let my bro drive my car and when he returned it there was something hanging from the front under the bumper. i looked at it the best i could cause we just got 8 inches of snow and it looks like it is just a plastic skidplate but i am not sure. i used to be a mechanic but never worked on imports, only 4x4 trucks so i am a lil confused. i am wondering, 1 if it evens needs to stay on, 2 what it exactly is, and 3 how much do you think it will be to fix.

It's a sound dampening pan. It smooths out the underside of the car and quiets it. You don't 'need' it, but it's good to have.

anyone know about how much for a new one

is it a big plastic piece?

Usually around 200-300.  I would just take it off thou.  Makes it easier to work on the car.

yeah its a big plastic piece

Yeah thats the sound absorber pan.  Also known as a belly pan.

The belly pan is not necessary, but it's good to have, especially if you're going to be driving in sub-standard weather.  If yours is cracked or broken, you can probably pick one up at a junkyard for pretty cheap.

it helps force air through the engine bay and out the back, increases airdynamics, sound and protects your oil pan (not much)
 
cant be too much at audi, get the part # from them then look it up online

Its around $300 at the dealer plus $4 per little clip. They are cheaper online. I found one for $164, can't remember where though.