It shouldn't be expensive if you're lucky enough to find a very reputable dealership, but I would be afraid they would be inclined to tell you that it needed replacing, and replacing the throttle body is much more than $100.
You can do this really. Just locate the box where the air filter is. There should be a clamp that holds a hose to that, and a plug that's clipped in. To remove that plug you need to slide the red clip out, then the plug can be pulled out. Then the other end of that hose ties directly into the intake and has a clamp on that end. I THINK there are 2 plugs clipped into the throttle body, one is to the throttle position sensor, which would be a great time to replace that for cheap....but the screws tend to break, so you may need to be familiar with creative ways to remove scres if you do that too....I had to heat mine up with a torch to unscrew them with pliers.
then there are 4 bolts (actually 5, but one is to hold a bracket on one of the bolts) that remove the throttle body. you will notice a lot of black carbon built up in this. You may also see a small ridge of it where the butterfly is closest to the body....THAT's whats causing it to run rough at first idle I suspect. I used a whole can of throttle body cleaner on mine a couple of weeks ago....and a toothpick to get all the carbon out of it, including along the edge of the butterfly. Don't worry...you can just puch that open as needed to clean it. When it's clean, just reverse the order to put it all back together.
May also be a good time to pull the MAF sensor out of that rubber tube you removed...it's the thing that had the plug in it near the air filter box. You WILL NEED SPECIAL cleaning spray for that, it's called mass-air-flow cleaning spray.
When you're done, I'm certain you won't have spent $10 (unless you do replace the throttle position sensor) and about 1 hour....and it'll run much better.
