yes, replace 'em.
if your having it installed and buying off the internet, the installer WILL charge you more.
If you gonna buy your own equip and have someone else install, you are going to get charged more than usual. Most installers don't like this because the only money they make is in the labor.
You may want to look into going to your local audio store and asking them what they have and how much the whole package would be. You may get a rather good deal especially with how the economy is right now.