The garage door has too many parts to mention. I have personally replaced doors, motors, chains, but NEVER the springs. The springs are tightened extremely tight and are very dangerous if you do not know what you are doing.
That is the 1 item that I will never mess with!
Garage door maintenance is pretty easy.
All you need is some tools that you should have around the house and some WD-40 (or Garage door lubrication).
Step 1 - inspect the hinges and door itself
Step 2 - inspect tracks and clean if necessary
Step 3 - tighten any bolts or nuts that may have gotten loose over time
Step 4 - lubricate all hinges, locks, rollers and chain
Step 5 - open and close door once or twice to keep the lubrication in all small cracks
Quick and easy - it takes more time to inspect the items, than actually complete the lubrication process.
CLEAN YOUR GARAGE
Now this is something that I am adamant about; I clean my garage out frequently. It is the easiest way to keep pests out and inspect if any animals have gotten inside.
The last time I want to do is hear my wife scream because a mouse ran out from under her car due to a cracker left under the car by my daughter.