Courtney,
Those are way to easy to replace all by yourself. Plumbing might sound scary, or difficult but actually it is extremely easy to do. At least most of it is. I can't remember how many supply lines I have replaced over the years in this house not to mention installing new garbage disposals, new faucets, toilets, sinks, dishwashers. You name it. I just refuse to call out a plumber and pay them $80 for just walking through the front door when I can do it myself.
Make sure your water is turned off, then using a wrench turn the nut to the left . That takes it off. Take the old line to the hardware store with you for comparison and get the exact size. I would recommend getting one that is braided instead of a vinyl one as they rarely develop a leak. Buy some Teflon tape too.
When you put it back on, remove the tape from the threads of the part your going to screw in on to . Take off as much as you can, some you might not be able to get off. Wind some new tape three times around the threads then screw on the new supply line. Finger tight, then 1/4 turn with the wrench. Add thread to the other end if needed and screw it back into the valve. Remember only finger tight, then 1/4 turn of the wrench. Turn it to the right. The ends on the supply lines are made of brass which is very soft and if you over tighten them you will cause them to leak. When screwing them on or off remember, " Right to tight and Left to loose" Right to tighten them back on and Left to take them off! After, turn your water valve back on. It's easy and I know you can do it.
If you want to watch a how to video, go to Danco.com or ehow.com. Danco is a plumbing supplier to the major hardware stores and they used to supply our store. They have very good information videos to watch.