I had a wood double garage door and the bottom panels rotted from "rain splash" over a period of time. I think it cost me about $120-$150 to get those panels replaced and painted. They are starting to show rot again. This time I will just replace the whole thing with a metal garage door and be done with it.
Scooter, depending on the type of garage door you have, you may just be able to unbolt the bottom panels and replace them yourself for a significant cost savings.
Contact a garage door installation person. They regularly remove the wooden doors and install metal ones. If your panel is a standard size, the installer may give you a cheap price on replacing it with a good used one that was not the lower one down (which always is the one that gets rotted).
Otherwise, put in metal doors.