It's very important not to attempt major garage door repairs on your own, as they can lead to property damage, injuries, or even death.
Keep the garage door clean and in good repair. Wooden garage doors should be wiped down with a clean, dry cloth. Inspect the surface of the door to see if it needs repainting or staining, or if it shows any signs of insect damage. Patch any small holes with wood filler, lightly sand and then paint or stain as required.
The best type of lubricant is either a lithium grease or a silicone spray. A lithium grease product will form a moisture-reducing barrier and protect against friction. A silicone spray will have these qualities and will also help protect the components of your garage door.
It is indeed possible to replace just a single panel on a garage door. However, if multiple panels require replacement, it may be more cost-effective to replace the entire garage door.