Actually, more commonly when you hit a curb, it's the "rim" that is bent, and not the tire. As long as there are no obvious "bubbles" on the sidewall of the tire, it should be ok to reuse without any drivability issues. Seeing as this is a 2001, there is more than likely plenty of replacement rims at any local salvage yard. If you have just a plain "steel" rim with a hubcap, you're looking at around $30 for a new rim. If it's an aluminum rim, closer to $60-$75. Bring the new rim to any local garage, and have them mount the old tire to the new rim, and balance it- roughly $25, and you should be good as new.
I can't give you a price on "aftermarket" rims, as I have no access to that info, nor do I know which brand, etc. That you will have to check the manufacturer's website for.
As for whatever looks bent back there will need to be replaced, as this will effect alignment, and eventually will put extra stress on other suspension parts, causing them to fail prematurely. Below is a parts breakdown of your rear suspension. Pick out the part that looks bent to you, and i'll tell you what it is: