A garage door isn't a weekend project, and that's truer the newer the house. If your home was built close to 2002, you're likely working with a torsion spring system on a steel or insulated steel door, not the older extension-spring setups you'll find on houses from the 1960s and 70s elsewhere in the service area. Torsion springs are under real tension and they are not a DIY swap - a spring that lets go while you're adjusting it can break bones.
What you can reasonably do yourself: swap weatherstripping, lubricate rollers and hinges, tighten loose hardware, and test your opener's safety reverse. What you shouldn't: touch the torsion spring, wind or unwind cables, or try to square up a new door frame alone. If you're replacing a door outright rather than repairing one, the frame, header, and track alignment all have to be right the first time, or the opener will fight the door for years. That's the part worth paying for.