A garage door installation is not a good first DIY project, and it's worse on a house from this era. The door itself, the springs, and the track all have to be matched to each other and to an opening that may not be a standard modern width. Get the spring tension wrong on a heavier insulated door and you're looking at a cable that snaps under load, not a cosmetic mistake.
Where a Parkwood homeowner can reasonably do their own work: repainting an existing frame, swapping weatherstripping, or replacing a keypad. Full installation - setting a new door, track, and opener as a system - is where we'd tell you honestly it's not worth the risk to your hands or your framing. If your header turns out to need reinforcement, that's a call best made in person, not guessed at from a set of measurements you took yourself.